Praechlamys prima Friesenbichler et al., 2019
FRIESENBICHLER, E., M. HAUTMANN, E. GRADINARU & U. BUCHER. 2019. A highly diverse bivalve fauna from a Bithynian (Anisian, Middle Triassic) Tubiphytes‐microbial buildup in North Dobrogea (Romania). Papers in Palaeontology, 7 (1): 447-495, figs. 1-15. [p. 18, figs. 5J-5M]
2019 Chlamys (Praechlamys) prima Friesenbichler et al., 2019
Friesenbichler et al., 2019, figure 5.
|
«LSID. urn:lsid:zoobank.org:act:6EDFD317-06D9-4492-BF45-ED9A60654390
Derivation of name. Prima (Latin: the first) because this species is among the geologically earliest species of its genus.
Holotype. LPB IIIL 2062, one fragmented but otherwise well preserved LV.
Paratypes. LPB IIIL 2060, 2061, 2063–2065, 11 fragmented LVs, two internal moulds of LVs with some shell remains, one external mould of an LV and one unassigned valve.
Diagnosis. Praechlamys with approximately 30 radial ribs arranged in two ranks on the LV; anterior disc margin demarcated from anterior auricle by steep slope; shallow radial depression on posterior part of disc, where radial ornament becomes weaker than on main part of disc.
Description. Shell medium sized, moderately inflated, inequilateral, suborbicular, approximately as high as long, disc inflation decreases towards the posterior margin, separating morphologically the posterior part from the remaining disc; beak slightly prosogyrate, positioned in the middle of the straight dorsal margin and slightly projecting above it; auricles relatively large, anterior auricle with byssal sinus and larger than posterior one, clearly demarcated from disc by steep slope, posterior auricle truncated, obtuse and smaller than anterior one, clearly demarcated from disc but slope not as steep as anteriorly; up to 30 rounded first- and second-order ribs bearing small tubercles, getting broader towards the ventral margin, first-order ribs starting close to beak, second-order ribs starting slightly more distally, regularly intercalated, ribs denser but weaker on flat posterior part of disc, growth lines present, two weak ribs and several riblets on posterior auricle; internal structures not observed.
Remarks. The most similar species is Chlamys (Praechlamys) subdivisa (Bittner, 1901), which differs in having a tripartite division of the disc with a broad middle part and narrow radial depressions anteriorly and posteriorly. In the Dobrogea specimens a comparable depression/flattening of the disc occurs only posteriorly. Furthermore, C. (P.) subdivisa has 40–50 smooth ribs while C. (P.) prima has only c. 30 ribs. The intercalation of second- order ribs in C. (P.) subdivisa is more irregular and the posterior auricle lacks ribs or riblets.
Ecology. Specimens of Chlamys (Praechlamys) have a slightly less inflated RV with a deep byssal notch below the anterior auricle (as inferred from the presence of a byssal sinus in the LV). This suggests that these bivalves were epibyssate suspension feeders that rested pleurothetically on their RVs.»
EVELYN FRIESENBICHLER, MICHAEL HAUTMANN, EUGEN GRADINARU & UGO BUCHER, 2019
|