On the Apiotrigoniinae (Bivalvia, Trigoniida): Their Palaeobiogeography, Evolution and Classiﬁcation

N. Jb. Geol. Paläont. Abh. 300/2 (2021), 145–174 Article Stuttgart, May 2021

On the Apiotrigoniinae (Bivalvia, Trigoniida): their palaeobiogeography, evolution and classiﬁcation

Michael R. Cooper With 8 ﬁgures

Abstract: The Apiotrigoniinae are a predominantly Late Jurassic/Cretaceous group of mainly Tethyan and Boreal megatrigoniid bivalves. Tracking evolution reveals two phyletic lineages, the Heterotri- goniini which appeared in the Callovian, followed by the Apiotrigoniini in the Early Cretaceous, fol- lowing which the two groups evolved in parallel until their extinctions in the Maastrichtian. Forty-five nominal species are assessed and distributed among two tribes, two subtribes and 17 genera of which 11 are new. Two species are new, and a new genus is introduced for a vaugoniine homoeomorph.

Key words: Bivalvia, Trigoniida, Apiotrigoniinae, palaeobiogeography, phylogeny, classification, generic diagnoses, new taxa.

1. Introduction Apiotrigoniines bear a convergent resemblance to Jurassic Vaugoniinae (Myophorellidae), but differ in Agassiz (1840) introduced the section “Pennatae” for lacking beaded escutcheon and median carinae. Since a distinctive group of Cretaceous trigonias, for which V-shaped flank costae have evolved independently in much later the subgenus Megatrigonia (Apiotrigo other trigoniid lineages, the resemblance has result- nia) was introduced (Cox 1952). Soon thereafter, ed in the generic name Apiotrigonia being incorrect- Kobayashi (1954) elevated Apiotrigonia to the rank ly applied to a number of unrelated species. Of those of genus and placed it in his new subfamily Vaugo- originally assigned to the genus by Cox (1952), T. cal niinae, whereas Savel’ev (1958) presciently assigned deroni Castillo & Aguilera has since been trans- it to the Megatrigoniinae van Hoepen, 1929. Since ferred to Lambertrigonia (Cooper & Leanza 2019), then, Japanese workers have demonstrated that the T. chivensis Arkhanguelsky was re-assigned to the “Pennatae” constitute an important, long-lived and di- scabrotrigoniine Incomatiella (Cooper 2015a), T. ro versified component of the deeper- water offshore Cre- binaldina d’Orbigny was made type of the iotrigo- taceous benthos of the Oriental Province, for which niine Grandigonia (Cooper 2015c), and T. prognos Tashiro (1979) introduced the subfamily Apiotrigo- Paulcke the type of the pterotrigoniine Paulckella niinae. Tashiro’s work demonstrated that the group (Cooper et al. 1989). Of the species “undoubtedly” comprised two distinct phyletic lines which evolved identified asApiotrigonia by Tashiro (1972), T. cono in parallel for most of their existence, an observation, cardiformis Krauss is a Megatrigonia (Cooper 1991), which led Cooper (1991) to separate the tribe Hetero- T. condoni Packard a Columbitrigonia (Poulton trigoniini, later to be elevated to subfamily rank by 1977), T. pumila Nilsson an Oistotrigonia (Nakano Tashiro (1992). Cooper (2015a) united the subfam- 1957) and T. heterosculpta Stanton (1901) has been ilies Megatrigoniinae and Apiotrigoniinae as family transferred to the iotrigoniid genus Mayesella (Coo- Megatrigoniidae. per 2015c). Trigonia aequicostata Gabb (1864: 209,