Subphylum Homalozoa

STYLOPHORA-MITRATA - Description from Parsley, 1991. Ecology from Lefebvre, 2003

HOMOIOSTELEA Description from Parsley and Caster, 1965. Ecology from Kolata et al. 1977.

-Species Descriptions-
STYLOPHORA-MITRATA - Description from Parsley, 1991. Ecology from Lefebvre, 2003


Atelocystites cf. A. huxleyi Billings, 1858.

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.


  Atelocystites cf. A. huxleyi, MCZ 128266    

MCZ 128266: 8mm long



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HOMOIOSTELEA Description from Parsley and Caster, 1965. Ecology from Kolata et al. 1977.

Syringocrinus paradoxicus Billings, 1859

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).


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

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