[D] Bistahieversor sealeyi [sG] [T]
Describer
Carr & Williamson 2010
Time
Cretaceous Late Campanian
Classification
Saurischia Theropoda Tyrannosauria Tyrannosauroidea Tyrannosauridae
Diet
Carnivore
Fossilsite
Kirtland Formation, Hunter Wash, Bisti/De-na-zin Wilderness Area, northwestern New Mexico, US
Info
Abstract
Skeletal remains of Late Cretaceous (Campanian and Maastrichtian) tyrannosauroids are rare in southwestern North America (Carr and Williamson, 2000). Historically, the identity and diversity of southwestern tyrannosauroids was unclear because most of the fossils were isolated teeth and bones that are not diagnostic of known genera or species (Carr and Williamson, 2000). One partial skull and skeleton (OMNH 10131) from the upper Campanian of New Mexico was referred to the problematic tooth taxon Aublysodon cf. A. mirandus, a referral that was later falsified (Lehman and Carpenter, 1990; Carr and Williamson, 2004). Recently, two fairly complete skulls and skeletons were collected that enabled a review of tyrannosauroid fossils from the Campanian of New Mexico. These specimens provide the opportunity to accurately characterize Campanian tyrannosauroids of the southwest, and recover their phylogenetic relationships with wellknown species (Carr and Williamson, 2000). We report the presence of a new genus and species of deep-snouted tyrannosauroid from the upper Campanian of New Mexico, represented by several specimens including the partial skeleton of an adult and juvenile. This new taxon is part of the diversification of deepsnouted tyrannosauroids and emphasizes the high species richness of this widespread clade in the upper Campanian of western North America.
Holotype
NMMNH P-27469, an articulated skull and skeleton of an adult .
Etymology
Bistahi, place of the adobe formations (Navajo) in reference to the Bisti Wilderness Area; eversor, destroyer (Greek) in reference to the presumed predatory habits of the animal; Sealey, in reference toMr. Paul Sealey, Research Associate at the NMMNH, in recognition of his discovery of the holotype specimen.
Locality and horizon
locality L-3506, upper Campanian Hunter Wash Member, Kirtland Formation, Hunter Wash, Bisti/De-na-zin Wilderness Area, northwestern New Mexico
Referred Specimens
NMMNH P-25049, an incomplete skull and skeleton of a juvenile from Locality L-3097, upper Campanian, Farmington Member, Kirtland Formation, Pinabete Arroyo, northwestern New Mexico; NMMNH P-32824, rostral ramus of a right lacrimal, from locality L-4010, upper Campanian, Fruitland Formation, Hunter Wash, Bisti/De-na-zin Wilderness Area, northwestern New Mexico; OMNH 10131, a partial skull and skeleton of an adult, upper Campanian, upper Fruitland or lower Kirtland formations, Ah-shi-sle-pah Wash, northwestern New Mexico.
Diagnosis
Tyrannosauroid characterized by numerous cranial autapomorphies, including a forked palatal process of the premaxilla, supernumerary frontal processes of the nasal, lanceolate medial frontal processes of the nasal, a pneumatic foramen that pierces the supraorbital ramus of the lacrimal, a peaked sagittal crest, a dorsotemporal fossa that extends onto the lateral surface of the squamosal, a short prefrontal, a single pneumatic foramen in the palatine, a medial ridge on the angular for insertion into the surangular, a ventrolateral keel along the caudoventral margin of the mandible formed by the angular and prearticular, and a tall flange extending from the ventral margin of the rostral mylohyoid foramen of the splenial. The skull of the juvenile specimen (NMMNH P-25049) is badly damaged, but it is referable to Bistahieversor based on the presence of two supernumerary frontal processes on each nasal and a single pneumatic foramen in the palatine. In all other tyrannosauroids, juvenile and adult, the nasal overlaps the frontal with only two processes, and they possess two pneumatic foramina in the palatine (except one specimen of Albertosaurus sarcophagus, TMP 86.64.1, which has one foramen; Carr et al., 2005). The juvenile does not possess any characters that support a referral to another tyrannosauroid species. The juvenile specimen reveals that growth or size-related changes in the skull of Bistahieversor are consistent with differences between juveniles and adults of more derived species of tyrannosauroids, such as Albertosaurus libratus and Tyrannosaurus rex (Carr, 1999; Carr and Williamson, 2004). For example, the cranial ornamentation is elaborated in the adult, in which the cornual processes of the lacrimals and postorbitals are grossly enlarged relative to the juvenile. The presence of a pneumatic foramen in the supraorbital ramus of the lacrimal in the adult, which is absent in the juvenile, is consistent with the ontogenetic increase of pneumatization that is seen in other tyrannosauroids (Carr, 1999). Individual variation might be represented by features that are not seen in the ontogeny of other tyrannosauroids, such as a pneumatic foramen above the basipterygoid process in the juvenile that is absent from the adult, and an inflated body of the ectopterygoid in the juvenile that is not seen in the adult (Carr, 1999).
Carr & Williamson 2010
Time
Cretaceous Late Campanian
Classification
Saurischia Theropoda Tyrannosauria Tyrannosauroidea Tyrannosauridae
Diet
Carnivore
Fossilsite
Kirtland Formation, Hunter Wash, Bisti/De-na-zin Wilderness Area, northwestern New Mexico, US
Info
Abstract
Skeletal remains of Late Cretaceous (Campanian and Maastrichtian) tyrannosauroids are rare in southwestern North America (Carr and Williamson, 2000). Historically, the identity and diversity of southwestern tyrannosauroids was unclear because most of the fossils were isolated teeth and bones that are not diagnostic of known genera or species (Carr and Williamson, 2000). One partial skull and skeleton (OMNH 10131) from the upper Campanian of New Mexico was referred to the problematic tooth taxon Aublysodon cf. A. mirandus, a referral that was later falsified (Lehman and Carpenter, 1990; Carr and Williamson, 2004). Recently, two fairly complete skulls and skeletons were collected that enabled a review of tyrannosauroid fossils from the Campanian of New Mexico. These specimens provide the opportunity to accurately characterize Campanian tyrannosauroids of the southwest, and recover their phylogenetic relationships with wellknown species (Carr and Williamson, 2000). We report the presence of a new genus and species of deep-snouted tyrannosauroid from the upper Campanian of New Mexico, represented by several specimens including the partial skeleton of an adult and juvenile. This new taxon is part of the diversification of deepsnouted tyrannosauroids and emphasizes the high species richness of this widespread clade in the upper Campanian of western North America.
Holotype
NMMNH P-27469, an articulated skull and skeleton of an adult .
Etymology
Bistahi, place of the adobe formations (Navajo) in reference to the Bisti Wilderness Area; eversor, destroyer (Greek) in reference to the presumed predatory habits of the animal; Sealey, in reference toMr. Paul Sealey, Research Associate at the NMMNH, in recognition of his discovery of the holotype specimen.
Locality and horizon
locality L-3506, upper Campanian Hunter Wash Member, Kirtland Formation, Hunter Wash, Bisti/De-na-zin Wilderness Area, northwestern New Mexico
Referred Specimens
NMMNH P-25049, an incomplete skull and skeleton of a juvenile from Locality L-3097, upper Campanian, Farmington Member, Kirtland Formation, Pinabete Arroyo, northwestern New Mexico; NMMNH P-32824, rostral ramus of a right lacrimal, from locality L-4010, upper Campanian, Fruitland Formation, Hunter Wash, Bisti/De-na-zin Wilderness Area, northwestern New Mexico; OMNH 10131, a partial skull and skeleton of an adult, upper Campanian, upper Fruitland or lower Kirtland formations, Ah-shi-sle-pah Wash, northwestern New Mexico.
Diagnosis
Tyrannosauroid characterized by numerous cranial autapomorphies, including a forked palatal process of the premaxilla, supernumerary frontal processes of the nasal, lanceolate medial frontal processes of the nasal, a pneumatic foramen that pierces the supraorbital ramus of the lacrimal, a peaked sagittal crest, a dorsotemporal fossa that extends onto the lateral surface of the squamosal, a short prefrontal, a single pneumatic foramen in the palatine, a medial ridge on the angular for insertion into the surangular, a ventrolateral keel along the caudoventral margin of the mandible formed by the angular and prearticular, and a tall flange extending from the ventral margin of the rostral mylohyoid foramen of the splenial. The skull of the juvenile specimen (NMMNH P-25049) is badly damaged, but it is referable to Bistahieversor based on the presence of two supernumerary frontal processes on each nasal and a single pneumatic foramen in the palatine. In all other tyrannosauroids, juvenile and adult, the nasal overlaps the frontal with only two processes, and they possess two pneumatic foramina in the palatine (except one specimen of Albertosaurus sarcophagus, TMP 86.64.1, which has one foramen; Carr et al., 2005). The juvenile does not possess any characters that support a referral to another tyrannosauroid species. The juvenile specimen reveals that growth or size-related changes in the skull of Bistahieversor are consistent with differences between juveniles and adults of more derived species of tyrannosauroids, such as Albertosaurus libratus and Tyrannosaurus rex (Carr, 1999; Carr and Williamson, 2004). For example, the cranial ornamentation is elaborated in the adult, in which the cornual processes of the lacrimals and postorbitals are grossly enlarged relative to the juvenile. The presence of a pneumatic foramen in the supraorbital ramus of the lacrimal in the adult, which is absent in the juvenile, is consistent with the ontogenetic increase of pneumatization that is seen in other tyrannosauroids (Carr, 1999). Individual variation might be represented by features that are not seen in the ontogeny of other tyrannosauroids, such as a pneumatic foramen above the basipterygoid process in the juvenile that is absent from the adult, and an inflated body of the ectopterygoid in the juvenile that is not seen in the adult (Carr, 1999).