Tanycolagreus is a genus of Theropoda dinosaur from the Late Jurassic (Kimmeridgian to Tithonian) of the U.S. states of Wyoming, Utah, and Colorado.
Discovery and naming
In 1995 Western Paleontological Laboratories, Inc. uncovered the partial skeleton of a small theropod at the Bone Cabin Quarry West locality, Albany County, Wyoming, from the Salt Wash Member of the Morrison Formation, dating to the
Kimmeridgian-
Tithonian. At first the find was considered to be a specimen of
Coelurus[Miles, C.A., Carpenter K. and Cloward, K.C., 1998, "A new skeleton of Coelurus fragilis from the Morrison Formation of Wyoming", Journal of Vertebrate Paleontology 18(3): 64A] but subsequent study indicated it represented a species new to science, that in 2001 was announced to be named
Tanycolagreus topwilsoni. It was actually named and described by Kenneth Carpenter,
Clifford Miles and
Karen Cloward in 2005. The
etymology of the generic name
Tanycolagreus, suggested by Ben Creisler, is based upon the greater length of its forelimbs and hindlimbs compared to
Coelurus. It is derived from the
Ancient Greek prefix τανυ~,
tany~: 'long, stretched out', κῶλον,
kolon: 'limb' and ἀγρεύς,
agreus: 'hunter'. The specific name honors George Eugene "Top" Wilson, the father of a benefactor financially supporting the scientific research.
[Carpenter, K., Miles, C., and Cloward, K. (2005). "New small theropod from the Upper Jurassic Morrison Formation of Wyoming." in Carpenter, K. 2005. The Carnivorous Dinosaurs, Indiana University Press: 23-48]
The fossil,
holotype TPII 2000-09-29, was donated to science by an anonymous benefactor. It is part of the collection of Thanksgiving Point Institute, Inc. and displayed in the North American Museum of Ancient Life at Lehi, Utah. It includes an incomplete skull and
mandible (lower jaws) and much of the
skeleton, i.e. the parts behind the head. The skull of
Tanycolagreus is less well known than its postcranial
anatomy, and only the following elements have been found: left
nasal bone, left
Lacrimal bone, left
premaxilla and one premaxillary tooth, left
Postorbital bone, left quadratojugal, incomplete left
squamosal, right
Quadrate bone, right
splenial, left articular, and two cheek teeth. A paratype has been assigned to the species: specimen AMNH 587 consisting of an incomplete hand also collected from Bone Cabin Quarry and originally in 1903 by Henry Fairfield Osborn referred to
Ornitholestes hermanni.
[Osborn, Henry Fairfield, 1903, " Ornitholestes hermanni, a new compsognathoid dinosaur from the Upper Jurassic", Bulletin of the American Museum of Natural History 19(12): 459–464] Two other fossils have been referred to
Tanycolagreus: UUVP 2999, a
premaxilla, originally in 1974 referred to
Stokesosaurus clevelandi,
[Madsen, J., 1974, "A new theropod dinosaur from the Upper Jurassic of Utah", Journal of Paleontology, 48: 27-31] from the Cleveland-Lloyd Quarry of
Utah; and USNM 5737, a pair of distal
pubic bone from
Colorado earlier in 1920 by Charles Whitney Gilmore referred to
Coelurus.
[Gilmore, C.W., 1920, "Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus", Bulletin of the United States National Museum, 110: 1-154] These specimens are from the later Brushy Basin Member.
[
]
Tanycolagreus is present in stratigraphic zone 2 of the Morrison. Remains possibly referrable to Stokesosaurus have been recovered from stratigraphic zone 5 of the Morrison Formation.[Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329] A life restoration of Tanycolagreus is also on display at the North American Museum of Ancient Life, where it is portrayed as preying upon a small dinosaur, Nanosaurus agilis.
Description
Carpenter et al. (2005, pp. 43–44) determined that the holotype of Tanycolagreus represents a subadult individual which measured approximately long in life. However, one of the referred fossils, the premaxilla from the Cleveland-Lloyd Quarry, would have belonged to a larger individual, measuring long. In 2010 Gregory S. Paul estimated the weight of a four-meter-long animal at .[Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 124] It cannot be determined whether or not the Cleveland-Lloyd specimen represents a fully mature adult, so the upper size limit for the taxon remains unknown.
The head of Tanycolagreus is large, elongated and rectangular in profile due to a blunt snout. The leg is rather long and lightly built.[
]
Carpenter et al. (2005; pp. 27 & 29) diagnosed Tanycolagreus topwilsoni as follows: "Medium-sized Tetanurae having short, deep-bodied premaxilla pierced by narial foramen at base of nasal process, orbital process on postorbital, T-shaped quadratojugal, centrodiapophyseal lamina on dorsals. Differs from Coelurus in the absence of pleurocoel on anterior dorsals; posterior caudal prezygapophyses elongated to one-third centrum length, rather than short; straight, rather than sigmoidal, humeral shaft; bowed, rather than straight, radius; flat-bottomed rather than arced pubic foot; straight rather than sigmoidal femoral shaft; Metatarsal bones length subequal to humeral length, rather than 1.75 times humeral length. Differs from Ornitholestes in straight anterior margin of premaxilla, rather than rounded; T-shaped rather than L-shaped quadratojugal; elongate neural spine; posterior caudal prezygapophyses only one-third centrum length, rather than one-half centrum length; bowed, slender radius, rather than straight, robust radius".[
]
The single premaxillary tooth preserved with the holotype is badly damaged, but does exhibit the asymmetrical cross-section typical in theropod teeth; the cheek teeth are too poorly preserved to show any detail. In the foot the second toe is slightly hyperextendable but does not carry an enlarged claw.[
]
Classification
Carpenter e.a. originally assigned Tanycolagreus to the Coeluridae.[ Carpenter et al. (2005, p. 44) state that, of the other known Morrison theropods, this genus most closely resembles Coelurus, though it retains more "primitive" features. A detailed Phylogenetics analysis in 2007 by Philip Senter including Tanycolagreus showed it had a basal position in the Tyrannosauroidea.][Senter, P. (2007). "A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)", Journal of Systematic Palaeontology, 5(4): 429-463] Later analyses indicated a basal position in the Coelurosauria.[O.W.M. Rauhut, A.C. Milner, and S. Moore-Fay, 2010, "Cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi (Woodward, 1910) from the Middle Jurassic of England", Zoological Journal of the Linnean Society, 158(1): 155-195]
In their 2025 revision of the enigmatic Brazilian coelurosaurians Mirischia and Santanaraptor, Delcourt et al. consistently supported a Proceratosauridae clade. In equal-weight phylogenetic analyses, this group also tentatively included Tanycolagreus. However, in implied-weight phylogenetic analyses Tanycolagreus grouped with Mirischia, Santanaraptor and Juratyrant close to but not within Proceratosauridae. Unlike previous analyses, they found Proceratosauridae (and the Juratyrant clade in implied-weight analyses) to be a very ancient lineage of Maniraptoromorpha and outside Tyrannosauroidea.
