Non-marine fish of the late Santonian Milk River Formation of Alberta, Canada – evidence from vertebrate microfossil localities

Abstract

The diversity of fishes from the late Santonian Milk River Formation is investigated using a combined taxonomic/morphotype approach. Twenty-one taxa are present, including four elasmobranchs, seven basal actinopterygians, and of ten teleosts. The Milk River fish assemblage is more similar to assemblages from southern Utah than it is to the late Campanian assemblage of Alberta in the presence of the elasmobranch Lonchidion and a member of amiid subfamily Vidalamiinae, the relatively high abundance of the ostariophysan teleost U3/BvD, and the absence of sturgeon, Holostean A, Holostean B, and Coriops. This similarity is hypothesized to be the result of a northern shift in the distribution of these taxa during times of high global temperature, resulting in the presence of a “southern” faunal assemblage in Alberta during the late Santonian. In the relative abundance patterns of major groups of fish, the Milk River Formation assemblage is similar to late Campanian assemblages and different from those of late Maastrichtian in that amiids and lepsisoteids are of relatively low abundance. The abundance of acanthomorph teleosts in the Milk River Formation is similar to that of contemporaneous assemblages from Utah, which supports a pattern of increasing abundance of acanthomorphs from their first occurrence in non-marine vertebrate assemblages of the Western Interior in the Coniacian through to the end of the Cretaceous.

New occurrences of Belonostomus (Teleostomorpha: Aspidorhynchidae) from the Late Cretaceous of the North American Gulf Coastal Plain, USA

“…Scale bars equal 5 mm. Cook, 2016;Brinkman et al, 2017). The inclusion of the six new specimens reported here adds to the stratigraphic and paleobiogeographic records of Belonostomus in North America.…”

Two new plioplatecarpine mosasaurs (Mosasauridae; Plioplatecarpinae) of the genus <i>Ectenosaurus</i> from the Upper Cretaceous of North America

“…If this proves to be the case, the scarcity of Ectenosaurus specimens (and possibly the rarer Selmasaurus) in marine beds is comparable to infrequent discoveries of terrestrial, volant, and freshwater taxa recovered from the marine Mooreville Chalk and Niobrara Chalk (see Russell 1988 andIkejiri et al 2013 for reviews of non-marine vertebrates from the Niobrara Chalk and Mooreville Chalk, respectively). However, to date no Ectenosaurus specimens have been found in non-marine sediments, though non-marine strata coeval with the Mooreville Chalk and Niobrara Chalk have been heavily prospected for aquatic vertebrate fossils (e.g., the latest Santonian Deadhorse Coulee Member, Milk River Formation; Brinkman et al 2016).…”

A morphological study of vertebral centra in extant species of pike, Esox (Teleostei: Esociformes)

“…Tooth bearing elements were emphasized in initial studies, and several taxa were named on the basis of dentaries and pharyngeal elements (Estes 1969a, b;Estes and Hiatt 1978;Wilson et al 1992). More recently, it has been recognized that abdominal centra are also an important source of information on the diversity, distribution, and relative abundance of teleost fishes of this time (Brinkman and Neuman 2002;Neuman and Brinkman 2005;Brinkman et al 2013Brinkman et al , 2014Brinkman et al , 2017. In part, this is because abdominal centra tend to be well represented in vertebrate microfossil localities compared to tooth-bearing elements, likely because their nodular shape is favored by taphonomic processes.…”