Gephyrotes convexus (Martino, Emanuela Di & Rosso, Antonietta 2015)
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Ordo: Cheilostomatida
Familia: Cribrilinidae
Genus: Gephyrotes
Name
Gephyrotes convexus Canu & Bassler, 1920 – Wikispecies link – Pensoft Profile
- Gephyrotes convexus Martino, Emanuela Di, 2015, Zootaxa 3941: 273-273.
Materials Examined
Material examined.Cotypes: USNM64030 A–B, two specimens, Late Eocene, Alabama, USA. USNM64030 B is chosen as lectotype.
Description
Description. Colony encrusting unilaminar, multiserial (Figs 30–31). Ancestrula not observed; zooids in early astogeny smaller than later autozooids, lacking oral structures (Fig. 31). Autozooids distinct, with deep interzooidal furrows, arranged quincuncially, elliptical, slightly longer than broad (mean L/W = 1.14). Gymnocyst smooth, forming marginal portions of frontal shield, usually narrow laterally and more extensive proximally, often hidden in frontal view by adjacent zooids and visible only proximally as a rounded triangular area; larger and equally developed in early astogeny (Figs 31, 33). Frontal shield markedly convex, formed by 12–18 costae, not including the 2 distalmost pairs participating in the proximal peristomial rim. Costae 40–50 µm broad, apparently closely united along their length, with 3 small, circular, prominent pelmatidia on each. Proximal peristomial rim formed by conjunction of 2 pairs of raised costae, one pair originating from the bifurcation of those most proximal to orifice and projecting frontalwards, the second pair originating lateral to orifice as a continuation of avicularian rostra, if present; the collar-like structure exhibiting a single semicircular intercostal lacuna, centrally placed (Fig. 32). Primary orifice slightly broader than long, subquadrangular with concave proximal margin (Fig. 33); secondary orifice semilunar with markedly concave proximal margin (Fig. 32). Oral spine bases not observed. Ooecium subglobular, small, slightly wider than long, immersed in distal zooid (Fig. 32). Adventitious avicularia small, paired, teardrop-shaped with complete pivot bar (Figs 30, 32), laterally placed or transversely projecting across proximal end of orifice, proximomedially directed; associated with ooecium, lacking in non-reproductive zooids. Sporadic, hollow, tubular kenozooids along zooidal margins. Uniporous septula visible in inner vertical walls at colony margin (Fig. 33).
Discussion
Remarks. This species is readily distinguishable from the other encrusting congeners in the general appearance of the frontal shield, with numerous broad costae very close to each other. This feature is shared with G. quadriserialis, which has an erect growth morphology and well-developed marginal kenozooids. The presence of four oral spines, as reported by Canu & Bassler (1920), is rejected. The scars, sometimes observed at the oral margins, are interpreted as the breakage points of the collar-like structure.
Distribution
Distribution. Late Eocene of Alabama, USA (Fig. 1).
N (colonies, zooids)Mean SD Range Zooid length2, 10 530 62 441–602Zooid width2, 10 467 36 426–524Orifice length2, 6 97 4 94–100Orifice width2, 6 121 4 118–124Ovicell length2, 4 170 3 166–172Ovicell width2, 4 204 1 203–204Avicularia length2, 8 126 16 107–151Avicularia width2, 8 58 7 47–65 N, Number of colonies and number of zooids measured; SD, standard deviation.
Taxon Treatment
- Martino, Emanuela Di; Rosso, Antonietta; 2015: Revision of the bryozoan genus Gephyrotes Norman, 1903 (Cheilostomata, Cribrilinidae) with the description of two new taxa, Zootaxa 3941: 273-273. doi
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