Cliffs of Insanity (Cretaceous to of the United States)

Also known as COI

Where: Emery County, Utah (38.2° N, 109.6° W: paleocoordinates 39.8° N, 72.9° W)

• coordinate based on nearby landmark

When: Mussentuchit Member (Cedar Mountain Formation), Cenomanian to Cenomanian (100.5 - 89.8 Ma)

Environment/lithology: fluvial-lacustrine; fine-grained sandstone

• The microvertebrate fossils described here were recovered from a fine-grained sandstone sandwiched between siltstone-dominated units, approximately five meters below the contact with the overlying Naturita Formation. Five geologic samples above, within, and below the fossil layer were collected along a section ∼1 m high (Fig. 1E). These samples indicate the COI microfossil assemblage displays a coarsening upward sequence from siltstone below the fossil-bearing layer to a bentonitic, fine-grained sandstone within it and then a transition back to siltstone above the fossil-bearing layer, possibly representing an oxbow lake with an adjacent river migrating towards the lake. Precise locality information for this site is recorded at the NC Museum of Natural Sciences.

Size classes: macrofossils, mesofossils, microfossils

Preservation: trace

Collected in 2014

Collection methods: chemical, sieve, ,

• reposited at the North Carolina Museum of Natural Sciences

•Approximately 183 kg of in situ sediment was collected from a fossiliferous horizon ∼15 m in width and 30 cm thick. The sediment, composed principally of a gray, highly bentonitic mudstone, was screenwashed in loads of 1,000 g using nylon paint sieves and traditional nested sieves

Primary reference: H. M. Avrahami, T. A. Gates, A. B. Heckert, P. J. Makovicky, and L. E. Zanno. 2018. A new microvertebrate assemblage from the Mussentuchit Member, Cedar Mountain Formation: insights into the paleobiodiversity and paleobiogeography of early Late Cretaceous ecosystems in western North America. PeerJ 1-52 [E. Vlachos/E. Vlachos]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 200123: authorized by Evangelos Vlachos, entered by Evangelos Vlachos on 15.03.2019

Creative Commons license: CC BY (attribution)

Taxonomic list

 Neopterygii -
Neopterygii indet.
Approximately 112 teeth (Figs. 3A–3FF), 53 complete or partial scales (Figs. 3JJ–3LL), and additional skeletal and vertebral fragments were recovered representing Osteichthyes
 Salmoniformes - Enchodontidae
 Neopterygii -
 Amiiformes - Amiidae
Amiinae indet. Bonaparte 1837 bowfin
 Holostei -
Lepisosteiformes indet. Hay 1929 gar
Over 56 partial scales attributable to gars
 Lepisosteiformes - Lepisosteidae
Lepisosteidae indet. Cuvier 1825 gar
 Temnospondyli - Albanerpetontidae
Albanerpeton sp. Estes and Hoffstetter 1976 tetrapod
NCSM 33278 (Fig. 4) is a lissamphibian dentary bearing three complete teeth and one tooth fragment
 Testudines - Adocidae
Adocidae indet. Cope 1869 turtle
The COI contains shell fragments likely representing a new species of adocid
 Testudinata - Helochelydridae
Helochelydridae indet. Nopcsa 1928 turtle
The majority of turtle materials from the COI are referable to a new species of helochelydrid, previously referred to Naomichelys speciosa
 Avetheropoda -
Coelurosauria indet. Huene 1914 coelurosaur
NCSM 33268 (Figs. 9G–9N) is the largest theropod tooth recovered
 Avetheropoda - Dromaeosauridae
Dromaeosauridae indet. Colbert and Russell 1969 coelurosaur
Two teeth are assigned to Dromaeosauridae from the COI
Richardoestesia sp. Currie et al. 1990 coelurosaur
 Avetheropoda -
Paronychodon sp. Cope 1876 coelurosaur
Aves indet. Linnaeus 1758 bird
 Avetheropoda -
Tyrannosauroidea indet. Walker 1964 coelurosaur
NCSM 33276 (Figs. 9A–9F) is a premaxillary tooth and the only specimen that can be confidently referred to as a tyrannosauroid based on a suite of diagnostic characteristics
 Saurischia - Elongatoolithidae
Macroelongatoolithus sp. Li et al. 1995 theropod
ichnofossil, eggshell
 Ornithischia -
Ornithischia indet. ornithischian
 Neornithischia -
Hadrosauroidea indet. bird foot dinosaur
 Loricata -
Mesoeucrocodylia indet. Whetstone and Whybrow 1983 crocodilian
Teeth we identify as similar in morphology to bernissartids are apico-basally short, mesiodistally elongate, labiolingually compressed, and slightly reniform in occlusal view
 Loricata - Goniopholididae
cf. Dakotasuchus sp. Mehl 1941 crocodilian
 Squamata -
Squamata indet. Oppel 1811 squamates
Scincomorpha indet. lizard
NCSM 33293 is a scincomorphan (paramacellodid–cordylid grade) (R. Nydam, 2018, personal communication) with subpleurodont implantation
 Theriiformes -
Sinbadelphys schmidti Cifelli 2004 metatherian
Marsupialia indet. Illiger 1811 marsupial