Aduncodina unicosta Ding, 1983
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publication ID |
https://doi.org/ 10.1186/s13358-022-00259-x |
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persistent identifier |
https://treatment.plazi.org/id/038B1D1D-645B-FF82-FCA1-EFBBD128FCE7 |
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treatment provided by |
Felipe |
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scientific name |
Aduncodina unicosta Ding, 1983 |
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Aduncodina unicosta Ding, 1983
Fig. 24R–T View Fig
*1983 Aduncodina unicosta n. sp.; Ding, p.41, pl. 6, figs. 10–14, 20(?)-21.
1983 Cornudina cf. oezdemirae Gedik ; Ding, p. 42, pl. 7, figs. 25–26
1998 Aduncodina unicosta Ding ; Koike, p. 126, fig. 8.4–8.26.
2007 Aduncodina unicosta Ding ; Orchard, p. 96, fig. 2 2019 Aduncodina unicosta Ding ; Chen et al., figs. 5.7, 5.9, 6.6.
Number of specimens.> 30.
Description. Aduncodina unicosta has been reconstructed by Koike (1998) as a quadrimembrate skeletal apparatus encompassing only Sa–c (S 1–3) and M nongeniculate coniform elements. Te adenticulated, subsymmetrical element is regarded by Koike as the M element, whereas the denticulated elements are interpreted as pertaining to the S series, the subsymmetrical one that bears one denticle being the Sa (S 0), the asymmetric one that bears up to three antero-lateral, hook-like denticles (in Zhao’s collections, those elements may bear up to five denticles, see his Ph.D thesis, 2005) and whose basal cavity is triangular in cross-section being the Sb (S 1) and the asymmetric one with a lenticular basal cavity being the Sc (S 2). All elements share common characteristics such as a thin wall, a relatively large and long and laterally flattened basal cavity. Te slender cusp is suberect and subcircular in cross-section. Basal margin weakly to strongly convex anteriorly.
Remarks. We agree with Orchard (2007) that the reconstruction by Koike (1998) might be incomplete. Neostrachanognathus was also reconstructed by Koike (ibid) as including only coniform elements but later revised by Agematsu et al. (2008) with convincing evidence from natural assemblages as including also complex multidenticulate (bipennate) elements in the S positions. It is to be expected that Aduncodina too may possess complex multidenticulate elements in those positions. Te morphology of the illustrated elements of Aduncodina unicosta resembles that of Ordovician forms such as Strachanognathus . In common with Neostrachanognathus , Aduncodina has a suite of denticulate elements, identified as Sb and Sc by Koike (1998), with an antero-lateral denticle or process that is directed posteriorward at its base, which is a feature of the Cornudininae (Orchard, 2007).
Occurrence. Japan: Taho Formation, co-occurrence with Ic. collinsoni in the Spathian substage ( Koike, 1998); China: Biandanshan formation, co-occurrence with Ic. collinsoni and Tr. homeri, Mountain Majiashan of Chaoxian, Anhui province ( Ding, 1983). Oman: Wadi Bani Khalid section, Spathian between UA 10 and UA 11 ( Chen et al., 2019).
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