On the Buchotrigoniidae (Cretaceous Trigoniida), Their Palaeobiogeography, Evolution and Classiﬁcation

N. Jb. Geol. Paläont. Abh. 301/2 (2021), 119–134 Article Stuttgart, August 2021

On the Buchotrigoniidae (Cretaceous Trigoniida), their palaeobiogeography, evolution and classiﬁcation

Michael R. Cooper and Héctor A. Leanza With 5 ﬁgures

Abstract: The content, distribution, evolution and classification of the Cretaceous trigoniid family Buchotrigoniidae are assessed. The evolution of the group is tracked from its first appearance in the late Berriasian of Colombia until its final demise in the early Maastrichtian of Chile. Buchotrigoniids are a provincial group with their greatest diversity and longevity in the Andean Province. From there they spread northwards into the American Province during the Aptian and, simultaneously, migrated eastwards into western Tethys, reaching Central Asia by the late Cenomanian. The origin of the group remains problematical, and the long- held relationship with Syrotrigoniinae is regarded unproven. Due to a lack of beaded escutcheon and median carinae at any growth stage, Buchotrigoniidae are transferred from Myophorelloidea to Megatrigonioidea. As a result of phylogenetic analysis four genera are recognized, two of which are new.

Key words: Bivalvia, Trigonioida, Megatrigonioidea, Buchotrigoniidae, palaeobiogeography, evolution, classification, new taxa.

1. Introduction T. inca Fritzsche “variations within Buchotrigonia”, but these have since been transferred to Syrotrigonia Stoyanow (1949: 89) tentatively introduced the “sec- (Pérez & Reyes 1997). tion Abruptae” for a predominantly early Cretaceous In 1952, Cox introduced Syrotrigonia as a subgenus group of trigoniids whose classification had presented of Buchotrigonia and, on the basis of its flank chev- “… considerable problems”, since “… Little is known rons, Kobayashi & Mori (1955) placed Buchotrigo about the group connections”. Not much has changed nia in their newly introduced subfamily Vaugoniinae. over the last 70 years. The eponymous section name Nakano (1960) accepted this latter treatment, though derives from Trigonia abrupta von Buch (1839), a Savel’ev (1958) had earlier transferred Buchotrigo species from the late Barremian of Columbia for which nia to Quadratotrigoniinae, a group that also has flank Dietrich (1938) introduced the subgenus Trigonia chevrons in early growth. Subsequently, Nakano (Buchotrigonia). Although Stoyanow (1949: 83) (1968: 33) decided Buchotrigonia and Syrotrigonia did not use Dietrich’s subgenus, he maintained a were not monophyletic and looked to Linotrigonia “group of Trigonia abrupta” for the species hum boldti (= Oistotrigonia) for the origin of Buchotrigonia, and von Buch, lorenti Dana, forti Lissón and reesidei Vaugonia for the ancestry of Syrotrigonia but, curious- Stoyanow, regarding Trigonia pizcuetana Vilano- ly, transferred Buchotrigonia to the subfamily Myo- va y Piera, T. orbignyana Lissón and T. coquandi phorellinae. Pérez & Reyes (1986) retained the subge- Lissón) junior subjective synonyms of T. abrupta. In nera, placing them in Trigoniidae without assignment addition he considered T. flexicostata Fritzsche and to a subfamily. H.A. Leanza (1993: 57) considered