Pronunciation: SEE-dar-PEL-tuh
Meaning: Cedar Shield
Author/s: Carpenter et al. (2001)
Synonyms: None known
First Discovery: Utah, USA
Acta Ordinal: #489
Cedarpelta bilbeyhallorum
Gastonia aside, Cedarpelta bilbeyhallorum is the oldest ankylosaurid from North America and the most primitive known member of Ankylosauridae—the club-tailed ankylosaurs. Yet according to name-coining-author Ken Carpenter's 2001 diagnosis, it's most closely related to the Asian Gobisaurus domoculus and Shamosaurus scutatus. It's also one of the largest ankylosaurids, rivalling Ankylosaurus magniventris itself, size-wise, but it hasn't been without its doubters.
A particularly long snout, weakly ornamented skull, and no evidence of a "typical" ankylosaurid ankylosaur clubbed tail led Vickaryous et al. (2004) to suspect an affinity with the spike-shouldered nodosaurids: the ankylosaurs with, well, particularly long snouts and weakly ornamented skulls, that lack clubbed tails. As it happens, no pre-Campanian-aged North American ankylosaurids appear to have had a tail club, and the remains of Cedarpelta lack a tail end that could've held a club anyway. It does, however, sport a closed "window" on the side of the skull behind the eye socket (the lateral temporal fenestra), which is only known in ankylosaurids, so Carpenter's original identification was right on the money.
The paratype skull of Cedarpelta was discovered disarticulated while the holotype was missing its lower jaw and most of a snout. But far from being a bad thing, it afforded palaeontologists the first glimpse inside of an ankylosaurid noggin and the opportunity to study its individual bones, which, until this point, had always been part of an impenetrable, heavily fused unit.
A particularly long snout, weakly ornamented skull, and no evidence of a "typical" ankylosaurid ankylosaur clubbed tail led Vickaryous et al. (2004) to suspect an affinity with the spike-shouldered nodosaurids: the ankylosaurs with, well, particularly long snouts and weakly ornamented skulls, that lack clubbed tails. As it happens, no pre-Campanian-aged North American ankylosaurids appear to have had a tail club, and the remains of Cedarpelta lack a tail end that could've held a club anyway. It does, however, sport a closed "window" on the side of the skull behind the eye socket (the lateral temporal fenestra), which is only known in ankylosaurids, so Carpenter's original identification was right on the money.
The paratype skull of Cedarpelta was discovered disarticulated while the holotype was missing its lower jaw and most of a snout. But far from being a bad thing, it afforded palaeontologists the first glimpse inside of an ankylosaurid noggin and the opportunity to study its individual bones, which, until this point, had always been part of an impenetrable, heavily fused unit.
(Bilbey and Hall's Cedar Mountain shield)
Etymology
Cedarpelta is derived from "Cedar" (for the Cedar Park Formation) and the Greek "pelte" (shield) in reference to its place of discovery and its armour.
The species epithet,
bilbeyhallorum (bil-bee-haw-LOR-um), honours Sue Ann Bilbey and Evan Hall who discovered the type locality.
Discovery
The first fossils of Cedarpelta were discovered at the Price River I site in the base of the Mussentuchit Member (previously thought to be the top of the older Ruby Ranch Member) of the Cedar Mountain Formation, Carbon County, Utah, USA, by Sue Ann Bilbey and Evan Hall.
The holotype (CEUM 12360) is a partial skull, lacking the lower jaw. Some elements resemble their counterparts in Stegosaurus, whereas others differ considerably. Paratypes, from the same quarry, consist of fourteen disarticulated skull bones (CEUM 10405, CEUM 10410, CEUM 10421, CEUM 10560, CEUM 10352, CEUM 10598, CEUM 10325, CEUM 10332, CEUM 10345, CEUM 10417, CEUM 10561, CEUM 10267, CEUM 10270, CEUM 10529), a partial neck vertebra CEUM 11288 and two neck ribs (CEUM 10248, CEUM 10445), four partial back vertebrae (CEUM 10258, CEUM 10409, CEUM 10442, CEUM 10360), a "synsacrum" of two back vertebrae fused to the front end of a block of four hip vertebrae and one tail vertebrae fused to the back end (CEUM 12163), fourteen tail vertebrae (CEUM 10258, CEUM 10258, CEUM 10387, CEUM 10366, CEUM 10255, CEUM 10257, CEUM 10260, CEUM 10261, CEUM 10262, CEUM 10349, CEUM 10400, CEUM 10412, CEUM 10404, CEUM 10407), part of a right upper arm (CEUM 10258), an ulna bone from the forearm (CEUM 10425), three pelvic bones (CEUM 10266 = a left ischium, CEUM 10537 = a partial right ischium, CEUM10375 = a fragment of right ilium), nine hand bones (CEUM 10254, CEUM 10356, CEUM 10430, CEUM 10449, CEUM 10984, CEUM 10247, CEUM 9970, CEUM 9922, CEUM 10253), and thirteen pieces of assorted armour (CEUM 10526, CEUM 10359, CEUM 10394, CEUM 10431, CEUM 10459, CEUM 10248, CEUM 10359, CEUM 9960, CEUM 9962, CEUM 10548, CEUM 10414, CEUM 10441, CEUM 10338). Referred material (Carpenter et al. 2008) includes a neck vertebrae (CEUM 10396), a shoulder bone (CEUM 10371), two tail vertebrae (CEUM 10412, CEUM 10404), two upper arm bones (CEUM 10256, CEUM 11629), a hip bone (CEUM 10266), a thigh (CEUM 11334) and a shin (CEUM 11640), from the Price River 2 Quarry in the Mussentuchit Member of the Cedar Mountain Formation at Emery County, Utah: the same quarry that produced the holotype of Peloroplites cedrimontanus, and the remains of a brachiosaurid sauropod, an iguanodontid, a turtle, and a pterosaur.
