New Upper Cretaceous Microvertebrate Assemblage from the Williams Fork Formation, northwestern Colorado, U.S.A., and its Paleoenvironmental Implications

• DOI: 10.4202/app.00934.2021
• Publication Date: 2022-07-22T07:59:44Z
• Authors: Nickolas Brand; Andy Heckert; Israel Sanchez; John Foster; ReBecca Hunt-Foster; Jaelyn Eberle
• Keywords: Fork (system call); Assemblage (archaeology); Faunal assemblage

We describe a microvertebrate assemblage from the J&M site, of Upper Cretaceous (Campanian-Maastrichtian) Williams Fork Formation.Breakdown fossil bearing matrix was achieved with use heated dimethyl sulfoxide.Nine recovered taxa are new to both site and Formation.The sharks Lonchidion griffisi, Chiloscyllium sp., Cantioscyllium markaguntensis first non-batoid elasmobranchs reported Formation all represented by teeth.The rays Cristomylus Psuedomyledaphus also newly most common identifiable fossils were teeth indeterminate amiids, likely belonging Melvius.Osteichthyan include Paralbula, an pycnodontid tooth plate fragment, lungfish fragment.A teiid Peneteius is within Formation.Alligatoroid relatively extremely similar those contemporaneous durophage Brachychampsa but generically indeterminate.Terrestrial in much smaller numbers.Theropod dinosaur included isolated fragments dromaeosaurid and, possibly, Richardoestesia.We multituberculate metatherian form teeth.Some these known marine estuarine deposits given that so many associated have been together, it seems recording or influence at least part its depositional history.The mammalian suggest Judithian-Lancian age for while records squamate ray Myledaphus, may be temporally transitional between other late Campanian Maastrichtian-aged localities.