Phylum Echinodermata


Macroporaster matutinus

Macroporaster matutinus (Hall, 1847) - Descriptions by F. H. C. Hotchkiss
Asterias matutina Hall, 1847, p. 91, pl. 29, figs. 5a, 5b.
Coelaster matutina (Hall, 1847). d’Orbigny, 1850, p. 22.
Palasterina rigidus Billings [part], 1857, p. 291; Bolton, 1960, p. 91.
Petraster rigidus (Billings, 1857). Billings [part], 1858, p. 79, pl. 10, fig. 3b [not fig. 3a].
Asteracanthion matutina (Hall, 1847). Dujardin & Hupé, 1862, p. 342.
Palaeaster matutina (Hall, 1847). Hall, 1866, p. 3, p. 14, plate 9, fig. 2.
Palaeaster matutinus (Hall, 1847). White, 1896, p. 92; Whitfield, 1898, p. 24.
Hudsonaster matutinus (Hall, 1847). Schuchert, 1915, p. 57, pl. 2, fig. 2, pl. 3, fig. 2, pl. 5, fig. 1, pl. 5, fig. 2; Wilson, 1946, p. 42; Bolton, 1960, p. 91.
Macroporaster matutinus (Hall, 1847). Raymond, 1921, p. 167; Delo, 1934, p. 248; Spencer & Wright [part], 1966, p. U51 [but not fig. 48.1 = M. nylanderi]; Branstrattor, 1975, p. 62, pl. 1, fig. 2, pl. 1, fig. 3; Titus, 1986, p. 823; Blake, 1990, p. 352, fig. 3A-3C.
Protopalaeaster matutinus (Hall). Spencer, 1950, pp. 398, 405-406.

Description: Hudsonasteridae. Five arms. Small size. Approximate measurements of the three specimens MCZ 108055, MCZ 146701, and MCZ 146702: primary radius (R) from center of disk to arm tip, minor radius (r) from center of disk to interradial edge of disk, and width (w) of arm at base: R/r/w 7 mm/3 mm/2.5 mm (oral view); 13 mm/4.5 mm/5 mm (oral view); and 9 mm/3.5 mm/3.3 mm (aboral view). Heavily plated aborally and in the oral interbrachial area. The upper surfaces of the rays have five columns of ossicles. The carinals in the center are bounded on either side by the superomarginals, outside of which are the inferomarginals which border the rays. There are no accessory plates between the columns of ossicles. Spaces between carinal and superomarginal ossicles are implied papular openings (Branstrattor, 1975). The ossicles of adjoining superomarginal and inferomarginal columns alternate with each other. The upper surface of the disk has prominent radial and interradial plates that form a circlet. Highly prominent on the ventral surface is a single axillary marginal plate that fills the interbrachial arc. On the under surface of the ray the inferomarginal column borders the ambulacral ossicles. Adambulacrals are about one and one-half to two times as numerous as inferomarginals. The ambulacral groove is quite widely open in these specimens but is fairly closed in others (Blake 1990:fig. 3A). Biserial podial basins are prominent on each arm. The podial basins are floored by overlapping flanges of two consecutive ambulacral plates. The adambulacral ossicles are aligned one-for-one with the ambulacral ossicles. Notches at the junction of ambulacral and adjacent adambulacral columns may have housed podial ampullae; the notches are bounded by skeleton and do not reach the interior of the arm (Blake, 1990). All ossicles except the ambulacrals carried spines articulated upon spine-base pustules.

Ecology: The heavy skeleton may have imposed a limit on the body size by limiting the number of respiratory papulae (Branstrattor, 1975). A suggested ecology has been inferred from the skeletal mechanics by Blake (1990). Like modern asteroids, Macroporaster must have been subject to inversion by wave action or other external forces, and must have been able to right itself, which involves considerable twisting of the arms and disk. Accordingly, despite its massive and inflexible appearance, Macroporaster must have had both facultative flexibility and rigidity. Depressions on the sides of ossicles are interpreted as attachment areas for tissues linking the ossicles to each other. The ossicles are rather closely articulated which facilitates rigidity. The connective tissues could rigidly lock the marginal frame while still allowing the oral ossicles to move rather freely within the central portion of the disk during feeding. The axillary provided both support for overall body structure and contributed to the operation of the mouth frame. “Macroporaster is suggested to have selected an area of rich organic content, then locked the marginal frame and raked the sediment surface with the tube feet, concentrating organic materials such as epibenthic algal or bacterial films. Organic material was passed toward the mouth and shoveled through the mouth frame with a back-and-forth pumping action of the oral and axillary ossicles” (Blake 1990:354).

Notes: The type specimen of Hall (1847) “is from the thin shelly layers at Trenton Falls about midway of the rock.” MCZ No. 108055, 146701, 146702 are from Rathbone Brook, near Newport, Herkimer County, NY. MCZ 108056 is from Deerfield, Oneida County, NY. Spencer (1950) suggested that Macroporaster should lapse into the synonymy of Protopalaeaster, but this was not followed by Spencer & Wright (1966) or later authors.

MCZ 108055, 146701, 146702: Hypotypes, largest is 25mm wide
MCZ 108055, 146701, 146702: Hypotypes, largest is 25mm wide

Salteraster medusa

Salteraster medusa (Hudson, 1916) - Descriptions by F. H. C. Hotchkiss
Urasterella pulchella (Billings, 1857). Raymond, 1912, p. 106, pl. 6, fig. 1; Schuchert [part], 1915, p. 178, pl. 28, fig. 4, pl. 30, fig. 5; Delo, 1934, p. 248.
Urasterella medusa Hudson, 1916, p. 121, pl. 1-6; Spencer, 1918, p. 135, p. 146, pl. 8 fig. 4, 7; Delo 1934, p. 248; Hotchkiss, Prokop & Petr, 1999, p. 190.

Description: Five arms. The disk lacks interbrachial development. The width of the base of the arms determines the size of the mouth-disk region. The arms are fairly long, gently tapering and flexible. Arms rounded in section (MCZ 108087). Approximate measurements of primary radius (R), minor radius (r) and width (w) of arm at base: R/r/w 28 mm/3.3 mm/4 mm [MCZ 108067] and 27 mm/3.5 mm/4.5 mm [MCZ 108069]. The dorsolateral and aboral plating of the arms is continuous onto the aboral disk. The plating is a dense array of subequal paxillae, each with well-formed base, shaft and spine tuft [the spine tuft and shaft are lost in weathering]. At the margins of the disk and rays the paxillar shaft is about twice as tall as the thickness of the paxillar base. The central portion of the disk is not sunken and has plates similar to the plates of the disk perimeter and the arm bases (MCZ 108069), or is sunken and with less evident plating than the arm bases (MCZ 108067), or is sunken and like a calcareous mat (MCZ 146700). The madreporite is aboral, interradial, between the perimeter and the center of the disk, and has typical furrows (MCZ 146700), but is not evident in most specimens. The carinal row of paxillar plates is not prominent or distinct from the other rows of aboral arm plates. The carinal paxillae, paxillar shaft and spine tuft are well shown in MCZ 146704. On each side of the ray, lateral to the carinals are four rows of dorsolateral plates that are arranged in a close-fitting diamond pattern which produces diagonal rows of plates on the sides of the ray. Between the lowermost dorsolateral plates and the adambulacral plates is a single row of marginal plates labeled inframarginals or inferomarginals by Schuchert (1915:pl. 30 fig. 5), Hudson (1916:129) and Spencer (1918:126). Ten marginals are adjacent to 14 adambulacrals (MCZ 108070). The marginals are paxillar; the paxillar base is longer (radially) than tall (dorsally). The marginals extend to the tip of the ray. In oral view there is no visible interbrachial arc of disk (MCZ 108068). No axillary plates are seen externally (in oral view), but they are seen internally as part of the mouth frame (weathering of the aboral surface exposes an aboral view of the mouth frame in MCZ 108087). In oral view only the ambulacral groove bordered by the adambulacral plates is visible (MCZ 108068): The ambulacral groove is very deep. The mouth angle plates are small triangular pieces not wider than the adambulacrals. The ambulacrals are deep in the groove and most are concealed by matrix. One arm has a distortion that shallows the groove and puts the ventral surface of the ambulacrals into view (MCZ 108068). The ambulacrals are closely packed with no spaces between them perradially. The ambulacrals have a proximal lobe that overlies the adjacent proximal ambulacral, and an abradial lobe that points toward a lobe or stem on the adambulacrals. A view of the inside of the ambulacral furrow made possible by a perradial split in the arm clearly shows abradial pockets between the ambulacrals and the adambulacrals (MCZ 108071, arm tip of the smaller specimen). These pockets almost certainly housed ampullae (Blake & Guensburg, 1988:Fig. 5A). The adambulacrals have furrow spines that are long and stout, ventral spines that are like short broad papillae bridging between successive adambulacrals, and ventral and abradial spines in double or triple rows (MCZ 108068). The adambulacrals margin the ambulacral groove which is in places widely open and in places closed to a miniscule gap by the adambulacrals. The adambulacrals imbricate adorally with substantial space between successive plates, or they imbricate distally and are close-fitting with no space between them. The distal face of each adambulacral has a large interadambulacral muscle depression. The abradial surfaces of the adambulacrals form the ventrolateral margin of the ray and displace upward the single row of marginal plates. The ambulacral plates overlie the adambulacral plates (MCZ 146704). The ambulacrals and adambulacrals are stout, tightly packed together, and fill the interior of the arm. The first three adambulacrals are beneath single ambulacrals; the ninth and more distal adambulacrals are lodged beneath two ambulacrals; between is a region of transition (MCZ 146704). In the holotype (MCZ 108087) nearly all the plates of the abactinal skeleton are weathered away, exposing the dorsal aspect of the ambulacral plates and the dorsal aspect of the mouth frame which Hudson called a ‘peristomial ring’. Key features of U. medusa noted by Hudson (1916:121, also plates 1, 2) that are unique to this internal view are: “Peristomial ring heavy. Axillary inframarginal prominent, its long axis parallel with the ring. First floor plates (peristomial) with radial diameters equal to the sum of those of the three following floor plates.” “The first floor plates make a radial (‘ambulacral’) jaw.” The axillary plates and the large ambulacral mouth plates are not visible externally in oral view. Comparison of the present state of the holotype with Hudson’s photographs (1916:plates 1, 2) shows that the internal axillary and some other parts of the fossil are missing. The space that was occuppied by the missing axillary is floored by the two triangular mouth angle plates, which explains why the axillary is not seen in oral view. The space for the axillary lines up with the row of paxillar marginals. Hudson’s photographs (1916: plates 1,2) are stereo-pairs and show the paxillar marginals abutting the internal axillary. The dorsal aspect of the ambulacral plates shows an absence of podial openings between the ambulacrals. The ambulacrals near to the mouth frame are oppositely placed, but the arrangement in the arms is for the greater part an alternate one (Hudson, 1916:127). The ambulacrals (in aboral view) are obtusely pointed at the perradial ends where they fit together closely (Raymond, 1912:105). This gives the ambulacrals a keeled convex angular shape and a zigzag median line of junction between the two columns of ambulacrals.

Juvenile and early growth stage of Salteraster medusa

Juvenile of Salteraster medusa [MCZ No. 108072]: The specimen is somewhat free of matrix and looks like a minute example of the larger specimens of S. medusa. The animal is folded ventrally near the perimeter of the disk, bringing one arm beneath the disk. As a result, only the abactinal surface of the disk and rays, and a bit of the lateral surface of the rays is visible. Overall size approximately 11 mm. Approximate measurements of R/r: 7.5 mm/2 mm. The folding of the specimen indicates some flexibility. The folding prevents a geometrical determination of the center of the disk. Only the disk perimeter and arm bases have knobs on the plates. There is a 'largest knob' near the presumed center of the disk, perhaps implying a central plate. The arms and the disk perimeter do not have unequivocally differentiated carinal plates. Rows of plates can be discerned, but otherwise the arrangement of the plates is not very clear. The plate boundaries are not clear; the high points of the plates have the greatest definition. There is a hint of a chevron arrangement, a hint of a diamond pattern. In one ray, three adjacent abactinal rows of plates appear to go to the tip of the ray. These are interpreted as a central row of carinals and adjacent rows of superomarginals. There is no row of plates between the carinals and the superomarginals. A ray on the fold axis shows a row of plates on its lower lateral surface that have greater distinctness and are more widely spaced than other plates. These are taken to be the inferomarginal plates, and beneath them can be seen a few faint adambulacrals. It is evident from the visibility of the adambulacrals in this lateral view of the ray that the adambulacrals form the lower lateral margin of the ray.

Notes: Prior catalog numbers for this specimen are MCZ No. 36 and MCZ No. 461. This specimen was remarked on by Schuchert (1915:178-179, MCZ No. 36) as the smallest specimen seen, a very young example, and as having the arrangement of the disk plates plainly preserved. In the present study the arrangement of the central disk plates was not discernable.

Early growth stage attributed by hypothesis to Salteraster medusa [MCZ No. 108066]: The specimen is free of matrix and can be viewed from both sides. The short rays have blunt, rounded tips. Approximate measurements of R/r/w: 2.3 mm/1.4 mm/1.6 mm. The aboral surface has many small plates, but the exact plating arrangement is indistinct due to lack of differentiation. The center of the disk is a depressed area approximately 0.6 mm diameter, bordered by five primary radial plates. Probably there are primary interradials between and slightly distal to the primary radials. An abactinal madreporite is presumed present but was not detected. A row of carinal plates is present. An inconspicuous row of plates on each side of the carinals was discerned. The plates of these rows are of about the same size as the carinal plates. The location of each row can be described as being between the carinals and the ambitals (pertaining to edge of body). Probably there is an inconspicuous terminal plate. In oral view: The ambulacral groove is open, but the ambulacral plates are indistinct. The interradial mouth angle plates are triangular, paired, and in line with the adambulacrals of the rays. There are six adambulacrals between the mouth angle plates and the indistinct presumed terminal plate; the distal sixth plate is notably smallest. The adambulacrals do not margin the ray. Indistinct plating adjacent to the adambulacrals forms the ambitus and interbrachial arc. If there is an axillary plate, it is indistinct and not detected. An important question is whether the ambitals seen in actinal view and the ambitals seen in abactinal view are the same or different plates. In the present study they are interpreted as being the same plates seen both from above and from below. If that is a correct assessment, then the ambital plates are inferomarginal plates, and the plates between the carinals and the ambitals are superomarginal plates. 

Notes: Prior catalog numbers for this specimen are MCZ No. 27 and MCZ No. 465. A label with prior number MCZ No. 465 states Young of Urasterella pulchellaC. Schuchert ident., but this specimen was not included in the materials of U. pulchella listed by Schuchert (1915:178). In this study, Schuchert's unpublished identification as U. pulchella is used as a working hypothesis, except that the Trenton Falls U. pulchella material is reidentified as Salteraster medusa . Identification as a urasterellid early growth stage is supported by the undifferentiated appearance of the plates of the dorsal surface [not the stout plates of the 'hudsonasterid' look], the lack of visible axillary plates on the oral surface, and especially that the adambulacral plates dominate as the most prominent plates of the oral surface. On the other hand, the general aspect is quite different from the juvenile specimen MCZ No. 108072 described above. Accordingly, attribution of this early growth stage specimen to S. medusa is uncertain because the associated specimens do not form a connected growth-series. This specimen is an important addition to the meager number of early growth stage specimens of Paleozoic stelleroids (Spencer 1916:figs. 35, 49, Blake 1990).

A label with prior number MCZ No. 27 has the identification Stenaster salteri [= S. obtusus ] and is annotated 'The smallest known fossil starfish and Schuchert'. The identification is crossed out as incorrect but is interesting because Shimer & Shrock (1944:211) included New York in their list of occurrences of S. salteri . A search of the literature did not confirm a New York record (Hotchkiss 1976:10), but it is not unreasonable that S. obtusus could be an undiscovered member of the Trenton Limestone, Trenton Falls , NY , fauna.

Ecology: The massive closely abutted ambulacral and adambulacral ossicles that alternated and interlocked in compression are highly suggestive of an asteroid that often is in a rigid state. At the same time, the rays could flex and twist as evidenced by the layout of the fossils. If overturned, the animal must have been able to right itself, indicating capability of interossicular displacement. The significance of the massive peristomial frame, with its large odontophore [internal axillary], to the interpretation of the ecology of this species is not yet understood. The size of S. medusa would permit it to gather prey smaller than itself such as diminutive mollusks, bryozoan twigs, etc., using its tube feet. The limited space inside the disk and arms suggests that no large items were ingested. It could have been a deposit feeder on epibenthic film. The starfish needed to move in order to obtain food. The ambulacrals had limited cross-furrow movement, but the adambulacrals were highly movable and could open up the ambulacral groove to expose the lateral cups for tube feet. Optimal foraging behavior is an important aspect of their feeding biology (Lawrence 1987:43). [Other references: Blake & Guensberg (1993) on Stibaraster; Jangoux (1982)]

Notes: The Walcott-Rust specimens identified as Urasterella pulchella by Schuchert (1915) and Delo (1934) are reidentified here as Urasterella medusa Hudson. Urasterella medusa is transferred to the genus Salteraster.

Hotchkiss et al. (1999:190) discussed the feature of alternating ambulacral plates (which in an asteroid should be opposite), with a perradial keel that makes a zigzag median suture. They suggested that the ambulacrals of this species are so solid-block-like and sutured together that the placement of the ambulacrals as either opposite or alternate is no longer an important constraint. They suggested that perhaps the shape of the sutures is determined in response to mechanical forces, and suggested comparison with the plates in regular echinoids that have convex outlines and zigzag sutures between columns of plates. They suggested that the convex angular sutures of this species are secondarily evolved and may be a useful taxonomic character.

MCZ 108072: Hypotype 10.5mm wide
MCZ 108072: Hypotype 10.5mm wide
MCZ 108087: Holotype, 37mm wide
MCZ 108087: Holotype, 37mm wide
MCZ 108069: Hypotype, 44.5mm wide
MCZ 108069: Hypotype, 44.5mm wide
MCZ 108066: Hypotype, 3mm wide
MCZ 108066: Hypotype, 3mm wide
MCZ 108067: Hypotype, 45mm wide
MCZ 108067: Hypotype, 45mm wide
MCZ 108068: Hypotype, 31.5mm wide
MCZ 108068: Hypotype, 31.5mm wide
MCZ 146703: 26mm long
MCZ 146703: 26mm long
MCZ 108070: Hypotype, 47.5mm wide
MCZ 108070: Hypotype, 47.5mm wide
MCZ 108070: Hypotype, 47.5mm wide
MCZ 108070: Hypotype, 47.5mm wide
MCZ 146700: 12.5mm wide
MCZ 146700: 12.5mm wide



Protasteridae n. sp.

Protasteridae n. sp. - Descriptions by F. H. C. Hotchkiss
Alepidaster n. sp. (?) Schuchert, 1915, p. 230; Delo, 1934, p. 248.
cf. Protasterina sp. Hotchkiss, 1970, p. 73.

Description: MCZ No. 108075: The specimen is in oral view. Measurements: R at least 19 mm; arm width with open ambulacral groove ca. 2.5 mm. Three of five mouth angle plates are exposed; the mouth frame is in the closed position so that the oral slits are small. In three arms seen in oral view, the ambulacral groove is widely exposed. The groove is very shallow as the laterals do not form a gutter. The ambulacrals alternate. The median suture is nearly straight. The lateral plates are thin, lacking a heavy vertical ridge; they have a thin ventral edge and a thin distal edge on which distally directed spines articulate. The side arm plates overlap by about 50% of their length. The spines of the distal edge are slender and overlap the spines of the next segment by about 20% of length or less. At least four distal spines. Indistinct leaf-like groove spines are recognized by comparison with MCZ 108076. The gap for ventral longitudinal muscles is about 40% of the segment interval.

MCZ No. 108076: Oral view. Disk diameter at least 5.5 mm (not fully exposed); R at least 15 mm; width of ray at edge of disk approximately 2 mm. Oral interradial areas show indistinct plating. The half-jaws on each side of an oral slit are composed of a mouth angle plate and two oral frame plates [possibly a single plate has weathered to look like two plates]. The oral slits end abruptly where the ambulacral groove begins. The proximal ambulacral plates are small, half the length of the succeeding ambulacrals. In one arm the ambulacral groove is widely open and the laterals do not form a gutter; the ambulacral plates actually stand proud of the lateral plates. The double row of ambulacral plates of each ray alternate across a fairly straight but slightly sinuous perradial suture. The ambulacrals are only approximately boot-shaped because the leg and the foot of the boot are about equidimensional. The cups for the tube feet are formed by both the ambulacral boot and the adjoining lateral plate. The ventral edge of the lateral plates is thin and carries three or four broad leaf-like groove spines. When the groove spines are splayed outward the cups for the tube feet are fully exposed. When splayed inward the cups for the tube feet are completely covered. The distal edge of the laterals is thin and carries at least three needle-like spines that do not quite overlap the spines of the next segment. Successive lateral plates do not notably overlap, and they lack a heavy vertical ridge.

MCZ No. 108077: The specimen shows the aboral side of a disk with the arm bases almost entirely missing. Disk diameter ca. 8 mm. The aboral integument is partly worn away to reveal the mouthframe and arm bases (inside the disk) in apical view. The disk integument is a thin granular calcareous mat that does not show discrete plating centrally, but there is a hint of discrete plating in the aboral interradial areas. Discrete plating is suggested also by spines lying in the aboral interradial areas. The half-jaws are quite long and slender; the oral gape is large; the oral slits are capacious. Proximal ambulacrals within the disk are beveled to accommodate the overriding action of the ossicles of the mouth frame during opening of the mouth aperture. 

Ecology: The protasterid ophiuroid Strataster devonicus (Devonian Silica Shale) was reconstructed with flat scapula-shaped groove spines because such spines were found loose on the bedding plane in close proximity with the holotype (Kesling 1972:12 and text-fig. 3). The Trenton Falls ophiuroids serve to definitely place leaf-shaped groove spines on a protasterid ophiuroid. Kesling & Chilman (1975:169 and plate 50) remark that the shale at the S. devonicus locality 'contains millions of these little flat spatula-shaped spines' and that 'the species appears to have been ideally suited to rake through the bottom debris with these large spines along its oral surface'. The unrelated ophiuroid Furcaster (belonging the to suborder Zeugophiurina with ambulacrals in pairs) also has leaf-shaped groove spines, illustrating parallel evolution. This complicates the identification of isolated spines of this type. Many such spines identified as Furcaster are beautifully illustrated by Boczarowski (2001). 

Notes: In this study the specimens are identified only to family level. The unique leaf-like groove spines in MCZ 108075 and 108076 mark this as an undescribed species. Specimen MCZ 108077 is presumed to be the same taxon by association. These specimens are under study by Alexander Glass as part of a larger study of Protasterina and of this family (personal communication April 2004). Schuchert (1915) thought that these specimens represented a new species of Alepidaster but they were reidentified as cf. Protasterina by Hotchkiss (1970). Alepidaster was considered a subjective junior synonym of Taeniaster by Hotchkiss (1970).

MCZ 108077: Syntype, 8mm wide
MCZ 108077: Syntype, 8mm wide
MCZ 108076: Syntype, 21mm wide
MCZ 108076: Syntype, 21mm wide
MCZ108075: Syntype, 25mm wide
MCZ108075: Syntype, 25mm wide


Amygdalocystites sp.

Amygdalocystites sp. Billings, 1854 - Description from Parsley and Mintz, 1975. Ecology from Guensburg, 1991
Amygdalocystites Billings, 1854, p. 270-271, fig. 4-9; Billings, 1856, p. 288-290; Billings, 1858, p. 63-65, pl. 6, fig. 1a-1e, 2a-2f, 3a, 6; Zittel, 1879, p. 413; Jaekel, 1900, p. 675, 676; Springer in Zittel, 1913, p. 151; Regnéll, 1945, p. 38, 39; Wilson, 1946, p. 9-11, pl. 1, fig. 1-4; Kesling, 1968, p.269, fig. 1-4; Parsley and Mintz, 1975, p. 44.
Ottawacystites. Wilson, 1946, p. 14, pl. 3, fig. 1.
Amygdalocystis Billings, 1854. Carpenter, 1891, v. 24, p. 27; Haeckel, 1896, p. 106; Bather, 1900, p. 57, fig. 19; Jaekel, 1918, p. 27.

Description and Occurrence: Rare in the Trenton Group. Theca transversely elliptical in cross-section, ovoid to almond-shaped in outline. Thecal plates numerous, hexagonal to octagonal, each plate with prominent prosopon rays radiating from an elevated central boss to the plate corners. Subepistereomal sutural pores well developed, usually adjacent to, or under, prosopon rays. Two uniserial arms recumbent, transverse. Each arm ossicle with free-standing pinnule; biserial covering plates on pinnules and over main food grooves. Periproct on anterior or posterior face. Column slightly tapering, composed of thin ossicles with crenulate sutures; proximal column sharply curved.

Ecology: Amydalocystites was a low-level, attached, rheophylic suspension feeder. Feeding style differed from that of typical stalked echinoderms such as crinoids, which have a circular or parabolic filtration fan. It is possible that the animal could have oriented itself for most effective streamlining with the stem and feeding structures parallel to prevailing currents. Down-current orientation was probably the most advantageous.

MCZ 133501: 48mm long
MCZ 133501: 48mm long
An example of the Amygdalocystites genus: reconstruction of Amygdalocystites florealis Billings after Parsley and Mintz, 1975
An example of the Amygdalocystites genus: reconstruction of Amygdalocystites florealis Billings after Parsley and Mintz, 1975


Cheirocystis anatiformis

Cheirocystis anatiformis (Hall, 1847) - Description by J. C. Brower
Echino-encrinites anatiformis Hall, 1847, p. 89-90, pl. 29, fig. 4a-4f.
Glyptocystites logani Billings, 1857, p. 282-283; 1858, p. 57-59, pl. 4, fig. 1a-1j; Chapman, 1861, p. 514, fig. 179; 1863, p. 198, fig. 179; Chapman, 1864, p. 170, fig. 179; Grabau and Shimer, 1910, p. 464.
Glyptocystites logani var. gracilis Billings, 1858, p. 59, pl. 4, fig. 2.
Echino-encrinites anatinaformis [sic] Billings, 1858, p. 58.
Glyptocystites anatifomis Miller, 1889, p. 269.
Homocystites anatiformis Whitfield, 1898, p. 26.
Homocystites anatiformis var. logani Whitfield, 1898, p. 26.
Chirocrinus anatiformis Jaekel, 1899, p. 221.
Chirocrinus logani Jaekel, 1899, p. 220.
Glyptocystis logani Springer, 1911, p. 45.
Cheirocrinus logani Bather, 1913, p. 441; Bassler, 1915, p. 213; Bassler and Moodey, 1943, p. 143.
Cheirocrinus logani var. gracilis Bather, 1913, p. 442.
Cheirocrinus logani gracilis Bassler, 1915, p. 213; Bassler and Moodey, 1943, p. 143.
Cheirocrinus anatiformis (Hall, 1847). Bassler, 1915, p. 212; Clark, 1919, p. 10-11, pl. 1, fig. 18; Bassler and Moodey, 1943, p. 142; Hussey, 1952, p. 34; Kesling, 1962, p. 4, fig. 1-4, pl. 1, fig. 1-7, pl. 2, fig. 1-7, pl. 3, fig. 1-5, pl. 4, fig. 1-9.
Cheirocrinus sp. Hussey, 1950, p. 13; 1952, p. 35.
Cheirocrinus plates, Hussey, 1952, p. 36.

Description and Occurrence: Rhombifera Cheirocrinidae. Common at various localities in the Trenton Group. Like some other abundant Trenton forms, C. anatiformis is most frequently associated with members of its own species. One individual from Walcott-Rust Quarry is located on a small slab with Cincinnaticrinus varibrachialus and the only known specimen of Amygdalocystites sp. Disarticulated plates and fragmented calyces of C. anatiformis are moderately common in beds with C. varibrachialus and Ectenocrinus simplex. Theca roughly cylindrical with rounded base and top; plates with prominent and sharp ridges. Pectinirhombs disjunct, often large, with raised centers. Large periproct visible in some specimens. Ambulacra short and restricted to oral area; brachioles biserial, unbranched, bearing four rows of large covering plates. Proximal stem tapering, consists of nodose and non-nodose plates; large axial canal present. Distal stem straight, made up of long and thin columnals with narrow axial canals. Holdfast not known.

Ecology: Although the holdfasts of C. anatiformis have not been seen, columns that are almost complete are common. The maximum known stem length is 37 mm. Hence, an elevation of about 50 mm above the substrate seems reasonable, and the animal clearly fed at a rather low level. C. anatiformis has food grooves that are about 0.7 mm wide which are the largest ones known in any of the Trenton pelmatozoans. Whether or not tubefeet were present in rhombiferans has been debated for many years. Brower (1999) gave a brief review and argued that tubefeet were present in rhombiferans such as Pleurocystites. Clearly, if C. anatiformis had tubefeet like those of crinoids, then it was certainly capable of catching large food particles.

MCZ 113643: 67mm long
MCZ 113643: 67mm long
MCZ 145749 and MCZ 145750: 36.5mm and 19mm long
MCZ 145749 and MCZ 145750: 36.5mm and 19mm long
MCZ 145751 and MCZ 145752: 28mm and 25mm long
MCZ 145751 and MCZ 145752: 28mm and 25mm long


Calceocrinus barrandii

Calceocrinus barrandii Walcott, 1884  – Descriptions by J. C. Brower
Calceocrinus barrandii Walcott, 1883, p. 6, Pl. 17, figs. 1-2 (adv. pub.); Walcott, 1884, p. 212, Pl. 17, figs. 1-2; Miller, S. A., 1889, p. 230; Bassler and Moodey, 1943, p. 469; Moore, 1962a, p. 21, figs. 7, no. D, fig. 11, no. C; Webster, 1973, p. 73; Brower, 1982, p. 92, fig. 32, no. I, figs. 33-38; Webster, 1988, p. 46.
Eucheirocrinus barrandii (Walcott, 1883). Bassler and Moodey, 1943, p. 469.

Description and Occurence: Disparida Calceocrinidae. Rare in the Trenton Group. The three known specimens have been found at Walcott-Rust Quarry where they are associated with Cincinnaticrinus varibrachialus and Ectenocrinus simplex. Cup and arms are unusual in having bilateral symmetry. Cup relatively slender; cup and arms with smooth plates. Arms nonpinnulate, uniserial; E ray arm long and unbranched; A and D ray arms have four slender axil arms with wide spaced branches; one or two nonaxillary plates present in each part of the main axil series. Column round, long and recumbent.

Ecology: Calceocrinids are unique crinoids because the stem is recumbent and runs along the seafloor. The cup is hinged between the basal and radial plates. To begin feeding, closing the hinge elevates the crown up roughly at a right angle to the stem and the arms are spread into a semicircular and somewhat curved filtration net with the food grooves facing down current. Calceocrinid crowns are located close to the seafloor, which minimizes the amount of competition with other crinoid species as well as with other stalked echinoderms. When not feeding, the hinge opens and the crown lies along the stem in the resting orientation, which is largely out of the zone of current flow. When resting the crinoid appears to be dead which is probably a defense mechanism to avoid predation. Although the food grooves are unknown, the thin arms are consistent with feeding on small food particles, which could consist of plankton and/or resuspended organic detritus.

MCZ 106419: Syntype, 22mm long crown
MCZ 106419: Syntype, 22mm long crown
MCZ 113420: Syntype, 31mm long
MCZ 113420: Syntype, 31mm long
living positions

Cincinnaticrinus varibrachialus

Cincinnaticrinus varibrachialus Warn and Strimple, 1977 – Descriptions by J. C. Brower
Heterocrinus heterodactylus Hall, 1866. Warn and Strimple, 1977, p. 41; Webster, 1986, p. 96.
Heterocrinus difficilis (Ulrich, Ms). Ruedemann, 1925, p. 70 (nomen nudum); Bassler and Moodey, 1943, p. 505; Warn and Strimple, 1977, p. 42; Webster, 1986, p. 96.
Heterocrinus tenuis Billings, 1857, p. 273; Billings, 1859, p. 50, Pl. 4, figs. 6a-6b; Bassler and Moodey, 1943, p. 506; Wilson, 1946, p. 32; Warn, 1973, p. 11, Pl. 1, fig. 1; Webster, 1973, p. 148; Warn and Strimple, 1977, p. 43; Webster, 1977, p. 96; Webster 1986, p. 96.
Ottawacrinus tenuis Jaekel, 1918, p. 85, fig. 79; Bassler and Moodey, 1943, p. 506.
Cincinnaticrinus varibrachialus Warn and Strimple, 1977, p. 41, pls. 3-5; figs. 8, 9 no. 2, 11, 13; Webster, 1986, p. 96; Kallmeyer and Donovan, 1998, p. 31, fig. 6, no. A.

Description and Occurrence: Disparida Cincinnaticrinidae. Ubiquitous at many localities in the Trenton Group. Cup conical with wide base; smooth or slightly nodose plates. Arms nonpinnulate, uniserial; branching isotomously on primibrachs; higher branches with bilateral heterotomy, proximal ramule on interray side; adults with up to 80 branches. Primibrachs typically 3 or 4; higher branches generally separated by 3 to 5 plates. Column with some prominent nodose plates, round to rounded sub-pentagonal outline; some columnals pentameric in proximal and middle stem; distal stem fully pentameric. “Lichenocrinid” type holdfast with round to lobate margins.

Ecology: Specimens are found attached to a wide range of hard objects including bryozoans, brachiopods, clams, cephalopods, trilobites, and pebbles as seen in one of the digital photographs. The stem length of juveniles ranges from 41 mm to 124 mm. Complete adults are not known but the longest preserved stem segment from the Trenton is 235 mm long so the mature columns were obviously somewhat longer. D. L. Meyer (2004, personal communication) has noted a specimen consisting of a crown and an incomplete stem with a length of 500 mm from the Kope Formation of the Cincinnati, Ohio region. The food grooves of juveniles and adults range from 0.185 mm to 0.215 mm in width so that the animals ate medium sized food particles. One preserved specimen suggests that the filtration net was held in a planar or parabolic fan.

Dendrocrinus sp. probably D. gregarius

Dendrocrinus sp. probably D. gregarius Billings, 1859 - Descriptions by J. C. Brower 
Dendrocrinus gregarius Billings, 1857, p. 265; Billings 1859a, p. 36, Pl. 3, figs. 1a-1c; Shumard, 1868, p. 365; Bigsby, 1868, p. 19; Miller, S. A., 1889, p. 238; Bassler, 1915, p. 396; Bassler and Moodey, 1943, p. 414; Wilson, 1946, p. 37, pl. 6, fig. 4; Webster, 1973, p. 103.

Description and Occurrence: Cladida Dendrocrinidae. Rare in the Trenton Group with only a single specimen found at the Walcott-Rust Quarry. Conical cup with smooth plates. Arms nonpinnulate, uniserial; arms branching isotomously on primibrachs and secundibrachs.

Ecology: Not known, the specimen is not complete enough to provide any useful data.

MCZ 113642: 20mm long
MCZ 113642: 20mm long

Ectenocrinus simplex (Hall, 1847)

Ectenocrinus simplex (Hall, 1847) - Descriptions by J. C. Brower
Heterocrinus simplex Hall, 1847, p. 280, pl. 76, figs. 2a-2; d’Orbigny, 1850, p. 24; Billings, 1857, p. 271; Hall, 1866, pl. 1, figs. 11-12. Owen in Shumard, 1866, p. 377; Shumard, 1868, p. 377; Bigsby, 1868, p. 20; Hall, 1872a, pl. 5, figs. 11-12; Hall, 1872b, pl. 5, figs. 11-12; Hall, 1873, p. 7, pl. 1, figs. 4a-4c, 5a-5b, 6a-6b; Quenstedt, 1885, p. 945, pl. 75, figs. 14, 16; Miller, S. A., 1889, p. 252; Dyche, 1892, p. 130; Grabau and Shimer, 1910, p. 502, fig. 1814; Bassler, 1915, p. 471; Bassler, 1938, p. 91; Bassler and Moodey, 1943, p. 443.
Heterocrinites simplex (Hall, 1847). Troost, 1850a, p. 61; Troost, 1850b, p. 419. 
Ectenocrinus (Heterocrinus) simplex (Hall, 1847). Wachsmuth and Springer, 1889b, p. 379; Bassler, 1915, p. 471. 
Ectenocrinus simplex (Hall, 1847). Miller, S. A., 1889, p. 242, fig. 296; Cumings, 1908, p. 720, pl. 4, figs. 10-10a; Bassler, 1915, p. 471; McFarlan, 1917, p. 68, pl. 9, fig. 21; Miller, A. M., 1919, pl. 22, fig. 3; Ulrich in Foerste, 1924, p. 94, fig. 11; Ruedemann, 1925, p. 69; Butts, C., 1941, p. 114, pl. 96, figs. 24-25; Bassler and Moodey, 1943, p. 443; Moore and Laudon, 1943b, p. 130, pl. 1, fig. 5; Moore and Laudon 1944, p. 145, pls. 52, fig. 7, pl. 53, fig. 8; Moore, 1962b, p. 31, pl. 1, fig. 2a, fig. 3, no. 2a; Jillson, 1963, p. 4, fig. 2; Webster, 1973, p. 119; Warn, 1975, p. 437, fig. 3; Warn and Strimple, 1977, p. 84, pls. 12-13, 14, figs. 1-7, 9-10, fig. 20; Moore and Lane in Moore and Teichert, 1978, p. T522, fig. 322, nos. 1a-1e; Smith, A. B., 1985, p. 170, pl. 7.4.15; Webster, 1986, p. 134; Brower, 1988, p. 919, fig. 2, no. 1; Webster, 1988, p. 80; Titus, 1989, p. 90, figs. 4.24-4.25, 5.9-5.10; Brower, 1992b, p. 979, figs. 8-11, 13; Webster, 1993, p. 53; Ausich, 1996b, p. 244, fig. 17-3, nos. 9-10; Brower, 1997, p. 442, figs. 1, 2, 8.
Ectenocrinus canadensis (Billings, 1857). Miller, S. A., 1889, p. 242; Wood, E., 1909, p. 22, pl. 4, fig. 10; Bassler, 1915, p. 471; Bassler and Moodey, 1943, p. 442; Wilson, A. E., 1946, p. 32, pl. 6, fig. 8; Moore, 1962b, p. 31, fig. 3, nos. 2b-2c; Webster, 1973, p. 119; Brower, 1992b, p. 979. 
Heterocrinus canadensis Billings, 1857a, p. 273; Billings, 1859a, p. 48, pl. 4, figs. 5a-5d; Shumard, 1868, p. 377; Bigsby, 1868, p. 20, 196; Miller, S. A., 1889, p. 252; Bassler, 1915, p. 471; Bassler and Moodey, 1943, p. 442. 
Ectenocrinus grandis (Meek, 1873). Miller, S. A., 1889, p. 242, fig. 295; Foerste, 1914, p. 124, pl. 1, figs. 8a-8d; Bassler, 1915, p. 471; McFarlan, 1917, p. 69, pl. 9, fig. 22; Miller, A. M., 1919, pl. 22, fig. 2; Bassler and Moodey, 1943, p. 442; Moore, 1962b, p. 24, pl. 1, figs. 2b-2c; Webster, 1973, p. 119; Moore and Lane in Moore and Teichert, 1978, p. T522, fig. 322, nos. 1f-1g; Webster, 1986, p. 134; Brower, 1992b, p. 979. 
Heterocrinus simplex var. grandis Meek, 1873a, p. 9, pl. 1, figs. 6-7; Miller, S. A., 1889, p. 252; Grabau and Shimer, 1910, p. 502, fig. 1814; Bassler, 1915, p. 471; Bassler and Moodey, 1943, p. 442.
Ectenocrinus raymondi Slocom, 1924, p. 337, pl. 29, figs. 5-9; Thomas and Ladd, 1926, p. 14, pl. 2, fig. 2; Bassler and Moodey, 1943, p. 442; Brower, 1992b, p. 979. 
Decadactylocrinites planus Owen, 1843, p. 1 (nomen nudum); Bassler, 1938, p. 84. 

Description and Occurrence: Disparida Homocrinidae. Ectenocrinus simplex and Cincinnatirinus varibrachialus are by far the most common crinoids in the Trenton Group and they are almost invariably collected together. Cup broadly conical with smooth plates. Arms nonpinnulate, uniserial; two primibrachs; primiaxillary gives rise to two “main arms” (secundibrachs) which consist of large proximal plates that taper distally; alternate “main arm” plates bear unbranched and thin ramules on opposite sides of the “main arms” with the proximal ramule in the interray position; adults with up to 260 arm branches. When the “main arms” are closed, the ramules are enclosed and hidden below the “main arms.” Column trimeric, round; some stem plates nodose; axial canal fully pentagonal. Holdfast is “lichenocrinid” type. Holdfasts of E. simplex and C. varibrachialus can be separated by the presence of trimeric as opposed to pentameric columnals. E. simplex differs from its ancestor E. triangulus Titus, 1989 in the Denley and Sugar River Limestones by its round stem and completely pentagonal axial canal. The ancestral axial canal varies from triangular to partly pentagonal in which two of the points are shorter than the other three and the stem is triangular to subround.

Ecology: Like C. varibrachialus, the lichenocrinid holdfast of E. simplex is attached to a wide range of hard objects. Complete specimens of E. simplex are not known but adults in the Trenton Group have attached incomplete stem segments ranging from 320 mm to 450 mm long, so the animals were located well above the seafloor. The available data suggest that on average, E. simplex lived at somewhat higher elevations than did C. varibrachialus in the Trenton oceans; nevertheless, the two taxa must have overlapped considerably with respect to distance above the seafloor. The filtration net of E. simplex was roughly conical in contrast to the more planar one seen in C. varibrachialus. The food grooves of juveniles and adults of E. simplex are 0.0947 and 0.16 mm wide, respectively, so that most of the food particles taken were slightly smaller than those utilized by C. varibrachialus. As with the elevations above the seafloor, the food particle sizes also intergrade with 32.5% and 75.1% overlap between the juveniles and adults of the two species, respectively. Clearly, E. simplex and C. varibrachialus would have competed if resources were limited in terms of food and/or space. When the arms are tightly closed, the soft parts and ramules are protected inside of relatively stout plates. This is interpreted as an adaptation to predators. The presence of regenerated arms in E. simplex and C. varibrachialus suggests that predation, perhaps by cephalopods and trilobites as well as other organisms, was moderately common in the Trenton seas.

Embyrocrinus problematicus

Embyrocrinus problematicus Hudson, 1917 - Descriptions by J. C. Brower
Embyrocrinus problematicus Hudson, 1917, p. 162, fig. 1,2; Bassler, 1938, p. 93; Bassler and Moodey, 1943, p. 445; Lane and Moore in Moore and Teichert, 1978, p. T596.

Description and Occurrence: Cladida Dendrocrinidae. Rare in the Trenton Group and is only known from a single specimen found at Walcott-Rust Quarry. Cup only 1.8 mm high, conical with smooth plates; four or five infrabasals, five basals, and five radials with narrow arm facets. Arms only represented by unbranched primibrachs. Columnals thin. The small size and construction of the cup indicates that this form is a juvenile dendrocrinid. It is probably a synonym of a previously described species and could be conspecific with the crinoid listed as Dendrocrinus sp. probably D. gregarius.

Ecology: Not known.

MCZ 144889: Holotype, 7mm long
MCZ 144889: Holotype, 7mm long
Provisional sketch showing plates on E. problematicus
Provisional sketch showing plates on E. problematicus

Iocrinus trentonensis

Iocrinus trentonensis Walcott, 1884 - Descriptions by J. C. Brower
Iocrinus trentonensis Walcott, 1883, p. 4, pl. 17, fig. 7-8 (adv. pub.); Walcott, 1884, p. 210, pls. 17-18; Miller, S. A., 1889, p. 257; Bassler, 1915, p. 668; Bassler and Moodey, 1943, p. 525.

Description and Occurrence: Disparida Iocrinidae. Common in the Trenton Group. I. trentonensis mainly occurs in monospecific associations but one specimen has been observed with Ectenocrinus simplex. Aboral cup conical, low and wide; plates covered with heavy ridges, sometimes with small rugose or pimple-like ornamentation. Arms uniserial, nonpinnulate; branching isotomously at various levels; generally 4 or 5 primibrachs; 5 to 7 secundibrachs; tertibrachs more variable, ranging from 6 to 16 plates; brachs commonly with distal flanges; adults with 40 to 50 branches. Tall anal sac is prominent in many specimens, covered with vertical and horizontal ridges; main anal sac plates short and wide, arranged in vertical columns or series of plates; small arched covering plates roof over areas between main anal series plates in the same column; construction of anal sac unique for Ordovician crinoids. Column pentagonal with some nodose plates. I. trentonensis is closely related to I. subcrassus from the Upper Ordovician in and around Cincinnati, Ohio. According to Walcott (1884), the Trenton crinoid is easily distinguished by its smaller size and less robust appearance. Adults of I. trentonensis are consistently smaller that those of I. subcrassus.

Ecology: Species of Iocrinus where the stem is known have a rather loose distal coil, which was presumably wrapped around some object on the seafloor or it may have formed an open coil directly on the substrate. One small specimen with a cup height of about 3.3 mm shows an attached incomplete stem segment that is about 120 mm long so the animal must have been at least that high above the seafloor. The wide food grooves (approximately 0.49 mm) and large covering plates denote that I. trentonensis caught relatively large food items with its big and widely spaced tubefeet. Several specimens are preserved with the arms spread, which demonstrates that I. trentonensis maintained a planar or parabolic filtration net. Iocrinids are generally thought to be relatively primitive disparids, but the anal sac is both specialized and unique which implies that I. trentonensis and related species are more derived than generally visualized.

Merocrinus corroboratus

Merocrinus corroboratus Walcott, 1884 - Descriptions by J. C. Brower
Merocrinus corroboratus Walcott, 1883. p. 4 (adv. pub.); Walcott, 1884, p. 210, pl. 17, fig. 6; Miller, 1889, p. 262; Bassler, 1915, p. 800; Bassler and Moodey, 1943, p. 562; Moore and Laudon, 1944, p. 155, pl. 53, fig. 17; Webster, 1973, p. 174.

Description and Occurrence: Cladida Merocrinidae. Rare in the Trenton Group. Aboral cup low and wide with smooth plates. Arms nonpinnulate, uniserial; arms slender, branching isotomously; primibrachs 6 or 7; secundibrachs 9 or 10; tertibrachs 10 or 11. Anal sac long, straight, slender and arm-like. Column round with short and smooth columnals; stem with little taper. M. corroboratus is basically the same as M. typus except for smaller size and more slender cup and arms. These differences could well be ontogenetic and later study may indicate that the two crinoids are conspecific.

Ecology: See Merocrinus typus.

MCZ 106416: Holotype, 48mm long
MCZ 106416: Holotype, 48mm long
Diagram of isotomous branching
Diagram of isotomous branching

Merocrinus retractilis

Merocrinus retractilis (Walcott, 1884) - Descriptions by J. C. Brower
Dendrocrinus retractilis Walcott, 1883 (adv. pub.); Walcott, 1884, p. 211, pl. 17, fig. 4; Miller, 1889, p. 239; Bassler, 1915, p. 397; Bassler and Moodey, 1943, p. 415.

Description and Occurrence: Cladida, Merocrinidae. Represented only by the holotype found at Walcott-Rust Quarry. Aboral cup low and wide; plates smooth. Arms nonpinnulate, uniserial; arms branch isotomously on primibrachs; higher branches follow bilateral heterotomy with the proximal unbranched ramule located in the interray position; primibrachs 5; secundibrachs 8 or 9; tertibrachs 10 or 11; quartibrachs 9 or 10. Anal tube long, slender, coiled in a loose spiral, which is unique. Column round with thin and smooth columnals; stem with little taper. M. retractilis can be separated from the other Trenton merocrinids by its heterotomous arm branching and spiral anal tube.

Ecology: See Merocrinus typus

MCZ 106418: Holotype, 73mm long
MCZ 106418: Holotype, 73mm long
Diagram showing heterotomous branching
Diagram showing heterotomous branching

Merocrinus typus

Merocrinus typus Walcott, 1884 - Descriptions by J. C. Brower
Merocrinus typus Walcott, 1883, p. 2 (adv. pub.); Walcott, 1884, p. 208, pl. 17, fig. 5; Miller, S. A., 1889, p. 262; Bassler, 1915, p. 801; Bassler, 1938, p. 132. Bassler and Moodey, 1943, p. 562; Moore and Laudon, 1943b, p. 132, pl. 3, fig. 3; Moore and Laudon, 1944, p. 155, pl. 53, fig. 16; Webster, 1973, p. 173; Moore and Lane in Moore and Teichert, 1978, p. T627, fig. 409, no. 3a; Webster, 1986, p. 203.

Description and Occurrence: Cladida Merocrinidae. Rare in the Trenton Group. Merocrinids at several Trenton localities occur in beds with Cincinnaticrinus varibrachialus and Ectenocrinus simplex. Same features as M. corroboratus except for larger size, comparatively wider cup, and more massive arms. As noted above, M. corroboratus may be a growth variant of and a junior synonym of M. typus.

Ecology: Complete stems and holdfasts are not known for any of the Trenton merocrinids so elevation above the seafloor is uncertain. Specimens from the Kope Formation of the Cincinnati, Ohio area have stems that are at least moderately long, and Meyer et al. (2002) reported an incomplete merocrinid stem segment with a length of 600 mm. The food grooves and covering plates are not preserved. However, the distal arms are all thin which is consistent with mainly feeding on small food particles.

MCZ 106415: Holotype, 24.5mm long
MCZ 106415: Holotype, 24.5mm long

Pycnocrinus argutus

Pycnocrinus argutus (Walcott, 1884) - Descriptions by J. C. Brower
Glyptocrinus argutus Walcott, 1883, p. 1 (adv. pub.); Walcott, 1884, p. 1, pl. 17, fig. 9; Miller, 1889, p. 248; Bassler, 1915, p. 1184; Bassler and Moodey, 1943, p. 684.
Stelidiocrinus argutus (?)(Walcott, 1883). Wachsmuth and Springer, 1897, p. 280, pl. 24, fig. 6; Bassler and Moodey, 1943, p. 684.
Stelidiocrinus argutus (Walcott, 1883). Bassler, 1915, p. 1184; Bassler and Moodey, 1943, p. 684.

Description and Occurrence: Camerata Glyptocrinidae. Rare in the Trenton Group. Crown small with maximum height of roughly 12 mm. Aboral cup with rounded sides; cup plates smooth to slightly swollen; median-ray ridges present; distal plates fixed into cup vary from primibrachs to proximal secundibrachs. Arms uniserial, with juvenile appearance, pinnulate; pinnules relatively short, stout and widely separated; arms branching on primibrach 2 and on secundibrachs well above the cup. Stem round to weakly pentagonal with some nodose plates. End of stem coiled.

Ecology: Two distal stem configurations may be present in P. argutus. The illustrated specimen exhibits a loose distal coil that either lay directly on the seafloor or was wrapped around a soft object on the seabed and the cup of this individual would have been at about the 14 mm elevation. Some of the stems that are tightly wrapped around the columns of other crinoids may also belong to P. argutus. The elevations of these animals would have depended on where the host stem was located. The food grooves have not been seen but the pinnules only range from about 0.1 mm to 0.2 mm wide which would restrict the species to small food items.

MCZ 113640: 25.5mm long
MCZ 113640: 25.5mm long
Diagram showing arm branching
Diagram showing arm branching


Rhaphanocrinus subnodosus

Rhaphanocrinus subnodosus (Walcott, 1883) - Descriptions by J. C. Brower
Glyptocrinus (?) subnodosus Walcott, 1883, p. 208 (adv. pub.); Walcott, 1884, p. 208, pl. 17, fig. 3; Miller, 1889, p. 248; Bassler, 1915, p. 1106; Bassler, 1938, p. 164; Bassler and Moodey, 1943, p. 661.
Rhaphanocrinus subnodosus (Walcott, 1883). Wachsmuth and Springer, 1885, p. 98 (320); Miller, 1889, p. 277; Wachsmuth and Springer, 1897, p. 259, pl. 11, fig. 2; Bassler, 1915, p. 1106; Bassler and Moodey, 1943, p. 661; Ubaghs in Moore and Teichert, 1978, p. T418, Fig. 228, no. 1a; Webster, 1986, p. 276.

Description and Occurrence: Camerata Archaeocrinidae. Common at some localities in the Trenton Group. Like Iocrinus trentonensis, R. subnodosus is mainly collected in monospecific associations. A single arm fragment is on a small slab with Ectenocrinus simplex. Aboral cup low and wide with rounded sides and numerous plates; cup plates with prominent median-ray and stellate ridges; moderate sized basal concavity with infrabasals and parts of basals; first interradials followed by two or three plates, many plates in higher ranges; numerous interbrachs between secundibrachs of same ray; secundibrachs form distal fixed brachs. Tegmen constructed of small irregular plates; small anal tube present. Arms uniserial, pinnulate, with numerous short and wide brachs; 10 unbranched arms present; pinnules long, slender and closely spaced. Stem round with some nodose plates. The most common fossils are cups and arm fragments.

Ecology: The stem length and elevation above the seafloor are not known. The food grooves are narrow (width 0.14 mm) and the covering plates are very fine which denotes that the animals subsisted on small food particles. Judging from the available material, the arms were quite flexible despite the fact that the arm articulations are purely ligamental as in other Ordovician crinoids. The dense filtration net with its close spaced pinnules and many small tube feet was probably parabolic like that of many living isocrinids.

MCZ 113448: 130.5mm long
MCZ 113448: 130.5mm long


(?) Edrioaster bigsbyi

(?) Edrioaster bigsbyi Hall, 1858 - Description from Regnéll, 1966

Description: Theca subcircular to subpentagonal, diameter 14 to 50 mm, height 0.25 to 0.5 mm of width; interambulacrals generally more of less pustulose or granulose, separated from central aboral region by frame of stouter plates; peripheral plates of aboral face variable in size, but not minute, central plates minute and tending to imbricate; ambulacra comparatively broad, raised or not raised above the general surface, A, B, D, E curving in a contrasolar direction, C in solar direction, or all curving solarly; small median cover plates may be present; peristome covered by solid tegmen of plates serially homologous with ambulacral cover plates; anus well defined, covered by variable number of irregular plates.

Ecology: Lived attached to some type of firm substrate such as a hardground or to a living or dead organism such as a brachiopod, bryozoan, or crinoid stem lying on the sea floor. Feed by bringing food to the mouth through a subvective system of ciliated grooves protected by cover plates.

MCZ 125601: 26mm wide
MCZ 125601: 26mm wide
Edrioasteriod (Echinozoan) morphology based on Edrioaster bigsbyi
Edrioasteriod (Echinozoan) morphology based on Edrioaster bigsbyi


Atelocystites cf. A. huxleyi

Atelocystites cf. A. huxleyi Billings, 1858 - Description from Parsley, 1991. Ecology from Lefebvre, 2003
Atelocystites huxleyi Billings, 1858, p. 72-74, fig. 4; Woodward, 1871, p. 71-73; Woodward, 1880, p. 193-201, pl. 6, fig. 1; Bassler, 1915, p. 88; Wilson, 1946, p. 7, 8, pl. 2, fig. 1-4; Caster, 1952, p. 29, fig. 29, fig. 2a, 2b; Kolata and Jollie, 1982, p. 640, 648; Parsley, 1991, p. 37, pl. 7, fig. 1-4.
Anomalocystites huxleyi (Billings, 1858). Miller, 1889, p. 224, 226.
Ateleocystis huxleyi (Billings, 1858). Haeckel, 1896, p. 41.
Atelecystis huxleyi (Billings, 1858). Bather, 1900, p. 51.

Description and Occurrence: Mitrate Carpoid. Common in the Trenton Group. The presence of a placocystitid plate, the exclusion of the median adaulacophoral plate from the proximal carapace margin, and the distinctive ornament on the adaulacophoral plates demonstrate that these specimens are truly assignable to Atelocystites. They seem to be quite close to the type species, A. huxleyi. Specimens show rather complete aulacophores. They are long, fully extended, and not reflexed back toward the theca as is typical with anomalocystitids, especially specimens preserved in younger strata. Also, the number of distal aulacophore segments in these specimens is estimated at between 25 and 30.

Ecology: The life orientation and mode of life of stylophorans is much debated. The alulacophore has been interpreted as equivalent to a pelmatozoan stem (Philip 1979; Kolata et al. 1991), a feeding arm (Ubaghs 1961; Parsley 1988), and even a chordate tail (Jefferies 1967; Cripps and Daley 1994) and these interpretations have lead to even more speculation on the supposed mode of life. Many authors have interpreted the flattened morphology of the stylophoran theca as an adaptation to bottom-dwelling, unattached, “flat-fish” mode of life (Termier and Termier 1948). Jefferies (1968, 1969, 1971) had proposed that juveniles were attached to the sea floor whereas adult froms were vagile organisms. Others have interpreted stylophorans as sessile epibenthic echinoderms (Bather 1913; Chauvel 1941; Ubaghs 1967, 1969). The possibility that stylophorans could swim by lateral undulation of their highly flexible appendage has also been proposed (Gislén 1930; Dehm 1934; Jefferies 1968, 1973; Jefferies and Prokop 1972; Parsley 1982, 1988, 2000; Cripps 1990). Some have also proposed that stylophorans were vagile epibenthic organisms using their aulacophore to crawl in the mud (Kirk 1911; Caster 1952; Gill and Caster 1960; Caster et al. 1961; Jefferies 1968, 1984, 1986; Philip 1981; Kolata and Jollie 1982; Frest 1988; Kolata et al. 1991; Woods and Jefferies 1992; Cripps and Daley 1994; Sutcliffe et al. 2000; Gee 2000). While others have suggested an infaunal mod of life for several mitrates possessing a theca with ratchet sculpture (cuesta-shaped ribs, asymmetrical tubercles), by analogy with other similar organisms (Jefferies and Prokop 1972; Jefferies and Lewis 1978; Jefferies 1982, 1984, 1986, 1999; Kolata and Jollie 1982; Savassi et al. 1982; Kolata et al. 1991; Ruta 1997; Ruta and Theron 1997; Ruta and Bartels 1998, Sutcliffe et al. 2000). Finally, Lefebvre (2003) suggests an infaunal mode of life with a “flat-surface down” orientation comparable to other stylophorans. They were probably mostly sessile with the theca downsteam, shallowly buried in the sediment, the arm resting over the sea floor, facing the current.

MCZ 128266: 8mm long
MCZ 128266: 8mm long


Syringocrinus paradoxicus

Syringocrinus paradoxicus Billings, 1859 - Description from Parsley and Caster, 1965. Ecology from Kolata et al. 1977
Syringocrinus paradoxicus Billings, 1859, p. 65-66, pl. 10, fig. 14; Miller, 1877, p. 92; Miller, 1889, p. 285; Gill and Caster, 1960, p. 17-20; Ubaghs, 1963, p. 1141; Parsley and Caster, 1965, p. 118.
Syringocrinus “paradoxus” Billings, 1859. Wachmuth and Springer, 1882, p. 411.
“Dendrocystis paradoxus” (Billlings, 1859). Bather, 1900, p. 48.
Dendrocystites(?) “paradoxica” (Billings, 1859). Bassler, 1915, p. 398; Nicoles, 1925, p. 90.
“Dendrocystis(?) paradoxica” (Billings, 1859). Bather, 1913, p. 371, 372, 397, 398, fig. 13, p. 396; Bather, 1928, p. 7-8.
Dendrocystites [paradoxicus] (Billings, 1859). Bassler, 1938, p. 9, 85.
Syringocrinus [paradoxicus] Billings, 1859. Springer in Zittel, 1913, p. 151; Jaekel, 1921, p. 124.; Hecker, 1940, p. 20, 62; Chauvel, 1941, p. 171, 241.
Dendrocystites paradoxicus (Billings, 1859). Bassler and Moody, 1943, p. 4, 149, 150, 192.
“Dendrocystites(?)” paradoxicus (Billings, 1859). Ragnéll, 1945, p. 195.
Dendrocystites(?) paradoxicus (Billings, 1859). Wilson, 1946, p. 3, 8.

Description and Occurrence: Solute Carpoid. Rare in the Trenton Group. Theca bilaterally symmetrical inflated and depressed. Plates are not evenly bilaterally paired and marginal plates large (probably 13 in number). The ventral surface has large polygonal plates bearing pebbly prosopon and the dorsal theca has many small polygonal plates. Proximal stele is composed of approximately 12 imbricating segments and the distal stele is asymmetrical. Syringocrinus paradoxicus differs from other Syringocrinus species in that the left plates are broader and shorter than the right plates with a sutural flange on the left series that parallels the distal suture, sharply rising to form a “plowshare-like” flange. It also has three dorsal plates between the right and left series, all tightly fused into a rigid zone, the dendrocystyloid.

Ecology: Had a “flat-fish” mode of life. Lived on the seafloor with the side with the small plates facing down on the substrate; the food groove on the arm also faces down and they probably ate organic detritus grubbed up from the bottom. These living habits are basically like pleurocystitid rhombiferans (Brower, 1999).

MCZ 113644: 62mm long
MCZ 113644: 62mm long
Reconstruction of Syringocrinus from Gill and Caster, 1960 (1a, obverse face, 1b, reverse side, 2a-b, showing detail of stele plates)
Reconstruction of Syringocrinus from Gill and Caster, 1960 (1a, obverse face, 1b, reverse side, 2a-b, showing detail of stele plates)