Neoschizodus laevigatus ( Goldfuss, 1837 )

Foster, William J., Danise, Silvia & Twitchett, Richard J., 2017, A silicified Early Triassic marine assemblage from Svalbard, Journal of Systematic Palaeontology 15 (10), pp. 851-877 : 864-865

publication ID

https://doi.org/ 10.1080/14772019.2016.1245680

publication LSID

lsid:zoobank.org:pub:3EBCAEF3-27C2-4216-9F18-89F195FA534F

DOI

https://doi.org/10.5281/zenodo.10903527

persistent identifier

https://treatment.plazi.org/id/C53B0B4D-805E-E824-6DFC-FAF78F8327B0

treatment provided by

Felipe

scientific name

Neoschizodus laevigatus ( Goldfuss, 1837 )
status

 

Neoschizodus laevigatus ( Goldfuss, 1837) View in CoL

( Fig. 9 View Figure 9 )

Material. Five specimens from LD-04 ( NHMUK PI MB 1251 ; NHMUK PE PEI 5489; NHMUK PE PEI 5519; NHMUK PE PEI 5522), and eight specimens from LD-05 ( NHMUK PE PEI 5476–5477 ; NHMUK PE PEI 5499; NHMUK PE PEI 5501; NHMUK PE PEI 5518; NHMUK PE PEI 5521). Fifty-nine prodissoconch valves from LD-04 ( NHMUK PI MB 1252 ; NHMUK PI MB 1254 ; NHMUK PI MB 1255–1260 ; NHMUK PE PEI 5480; NHMUK PE PEI 5484; NHMUK PE PEI 5486; NHMUK PE PEI 5511; NHMUK PE PEI 5513; NHMUK PE PEI 5520), and 14 prodissoconch valves from LD-05 ( NHMUK PI MB 1253 ; NHMUK PE PEI 5514) .

Description. Shell is trigonally subovate, equivalve, inflated below the umbo, inequilateral, slightly higher than long. Umbo is small and orthogyrate, with an elevated, subangular to rounded, umbonal ridge. Indistinct posterior ridge. Anterodorsal margin recurvate, passing to widely arched ventral margin, posterodorsal margin straight, entire inner margin smooth. Smooth sculpture except for faint concentric growth lines.

The larval shells have a similar external morphology to the adult shells, with a short and subumbonal hinge and short, narrow nymphs running down the anterior and posterior margins. The prodissoconch is smooth with fine concentric growth lines.

Remarks. Neoschizodus laevigatus is a cosmopolitan Early and Middle Triassic species with high variability in its morphological characters. The shell shape and indistinct posterior ridge mean that the present specimens agree with the characters of N. laevigatus , and similar specimens identified from the Early Triassic (e.g. Kumagae & Nakazawa 2009; Hautmann et al. 2011).

One of the adult specimens preserves a prodissoconch ( Fig. 9I View Figure 9 ) and its morphology is identical to that of the other prodissoconchs that were found as isolated specimens. The hinge plate of the prodissoconchs was not observed to be myophorian – instead the hinge dentition is typical of a taxodont – but it is not known how a myophorian hinge plate develops through ontogeny ( Newell & Boyd 1975). Hautmann & Nutzel (2005) suggested that, in bivalves, the presence of a small prodissoconch I and a relatively large prodissoconch II indicates a planktotrophic larval stage. Therefore, a planktotrophic larval stage is interpreted for these specimens.

Mode of life. Shallow infaunal, facultatively motile, unattached, suspension feeder ( Hautmann et al. 2013).

NHMUK

Natural History Museum, London

PI

Paleontological Institute

Kingdom

Animalia

Phylum

Mollusca

Class

Bivalvia

Order

Trigoniida

Family

Myophoriidae

Genus

Neoschizodus

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