The rudist Amphitriscoelus (Bivalvia-Hippuritacea) in the lower Cretaceous of southwestern Mexico

Abstract

The emended descriptions of the genus Amphitriscoelus and the species A. waringi Harris and Hodson are given, and a new species is proposed (A. pluriloculata). These rudist bivalves are derived from a thick Lower Cretaceous sequence of carbonate sediments interlayered with siliciclastic, volcaniclastic, and volcanic rocks in southwestern Mexico, near Huetamo, in the State of Michoacan. The species belong to a recently discovered rich fauna containing other rudists, nerineid gastropods, orbitolinid foraminifers, and calcareous algae. The fauna shows a close affinity with the Amphitriscoelus fauna of northern South America. Similar assemblages are also present in Texas, Cuba and other Mexican localities. The wide distribution of the fauna allows interpretation of paleogeographic relations among all the regions as well as interpretation of paleoecological similarities. The existence of an homogeneous large faunistic province during the Early Cretaceous is suggested.

Rudists and carbonate platforms in the Aptian: a case study on biotic interactions with ocean chemistry and climate

“…However, uncertainties remain over the exact stratigraphical range of these New World deposits within the Barremian to Bedoulian interval. The Jamaican and Cuban rudist‐bearing limestones may not even extend above the Barremian (Chartrousse & Masse, 1998a), while the primitive state of the embryonic apparatus in the orbitolinid Palorbitolina lenticularis that abundantly accompanies those of south‐western Mexico (Huetamo region): “indicates a basal early Aptian age for this population” (Alencaster & Pantoja‐Alor, 1996; based on study of the material by Rolf Schroeder and Antonietta Cherchi). Moreover, the Sligo Formation in the subsurface of Texas is overlain by open marine deposits of the Pearsall Formation, which contains the planktonic foraminifer Globuligerina hoterivica (Subbotina) together with Nannoconus bucheri Brönimann, both with a Hauterivian to Lower Aptian range (Scott & Hinote, 2007).…”

Palaeoecological significance of Barremian ammonite assemblages and facies variations from Southwest Mexico

“…The area comprises several environments of deposition within the Guerrero terrane (Campa & Coney 1983), affected by intermittent volcanic activities within a magmatic island arc (Mora Ân-Zenteno 1994). Superimposed to these events are the effects of a regional transgression that covered southern Mexico from the Late Jurassic to the Albian (Alencaster & Pantoja-Alor 1996). Excellent sections of Barremian strata belonging to the San Lucas Formation (Pantoja-Alor 1959) are well exposed in this part of Mexico, particularly in the Huetamo Region, which is the subject of this paper (Fig.…”

“…Studies regarding the evolution of the Barremian basins from Southwest Mexico (Garcia-Barrera & Pantoja-Alor 1991; Pantoja-Alor et al 1994;Alencaster & Pantoja-Alor 1996) consider the facies of the San Lucas Formation to be part of the transgressive systems tract of a second-order sequence of Late Jurassic±Albian age. This transgression eventually drowned the whole of Southwest Mexico.…”

There are rudists in Brazil! Derived examples of cf. Amphitriscoelus Harris and Hodson, 1922, in the Araripe Basin, north-east Brazil: Implications for dating of the fossil Lagerstätten of the Santana and Crato formations

“…6). Subsequently, it was discovered in the lower Aptian of Michoacán Huetamo, Mexico, where two species occur: A. waringi and A. pluriloculata Alencaster and Pantoja-Alor, 1996. Both species also occur near Michoacán in the San Lucas Valley, Mexico .…”