[Paleontology • 2017] Daspletosaurus horneri • A New Tyrannosaur with Evidence for Anagenesis and Crocodile-like Facial Sensory System

Daspletosaurus horneri 

 Carr, Varricchio, Sedlmayr, Roberts & Moore, 2017 

Holotype (MOR 590). Illustration: Dino Pulerà.
 DOI: 10.1038/srep44942  

Abstract

A new species of tyrannosaurid from the upper Two Medicine Formation of Montana supports the presence of a Laramidian anagenetic (ancestor-descendant) lineage of Late Cretaceous tyrannosaurids. In concert with other anagenetic lineages of dinosaurs from the same time and place, this suggests that anagenesis could have been a widespread mechanism generating species diversity amongst dinosaurs, and perhaps beyond. We studied the excellent fossil record of the tyrannosaurid to test that hypothesis. Phylogenetic analysis places this new taxon as the sister species to Daspletosaurus torosus. However, given their close phylogenetic relationship, geographic proximity, and temporal succession, where D. torosus (~76.7–75.2 Ma) precedes the younger new species (~75.1–74.4 Ma), we argue that the two forms most likely represent a single anagenetic lineage. Daspletosaurus was an important apex predator in the late Campanian dinosaur faunas of Laramidia; its absence from later units indicates it was extinct before Tyrannosaurus rex dispersed into Laramidia from Asia. In addition to its evolutionary implications, the texture of the facial bones of the new taxon, and other derived tyrannosauroids, indicates a scaly integument with high tactile sensitivity. Most significantly, the lower jaw shows evidence for neurovasculature that is also seen in birds.

Figure 1: Skull and jaws of the holotype (MOR 590) of Daspletosaurus horneri sp. nov.;
 (A) photograph and, (B) labeled line drawing of skull and jaws in left lateral view; (C) photograph and, (D) labeled line drawing of occiput and suspensorium in caudal view; (E) photograph and, (F) labeled line drawing of skull in dorsal view. Scale bars equal 10 cm. Abbreviations: MOR, Museum of the Rockies. 

Figure 2: Phylogenetic position and synapomorphies of Daspletosaurus, based on parsimony analysis.
 (A) Phylogenetic relationships of tyrannosaurines calibrated to geological time. Full consensus trees in Extended Data. Synapomorphies of the Daspletosaurus lineage from: (B) maxilla of MOR 1130; (C) lacrimal of MOR 1130; (D) postorbital of CMN 11594; (E) vomer of MOR 590; (F) palatine of MOR 1130; and (G) frontoparietal complex of MOR 590. Abbreviations: AMNH FARB, American Museum of Natural History, Fossil Amphibians, Reptiles, and Birds; As, Asia CMN, Canadian Museum of Nature; K/Pg, Cretaceous-Paleogene; LA, Laramidia; MOR, Museum of the Rockies. 

Figure 3: The growth series of Daspletosaurus horneri sp. nov., based on parsimony analysis.
 Unambiguously optimized derived phylogenetic characters were recovered as synontomorphies at two of the five growth stages, which are labeled at the corresponding numbers. Scale bar equals 10 cm. Abbreviations: AMNH FARB, American Museum of Natural History, Fossil Amphibians, Reptiles, and Birds; MOR, Museum of the Rockies. 

Theropoda Marsh, 1881

Tyrannosaurinae Matthew and Brown, 1922 (sensu Sereno et al., 2005)

Daspletosaurus Russell, 1970

Daspletosaurus. All species more closely related to Daspletosaurus torosus than to Tyrannosaurus rex.

Daspletosaurus horneri sp. nov.

Etymology: Horneri, Latinized form of Horner, in honor of Jack Horner, in recognition of his successful field program in the Two Medicine Formation that has recovered many new species of dinosaurs that are critical for our understanding of the palaeobiology of dinosaurs in Laramidia, support in the preparation and curation of these specimens, and to acknowledge that his mentoring efforts have launched many professional scientific careers.

Figure 4: The craniofacial epidermis of Daspletosaurus horneri sp. nov., based on comparison with its closest living relatives, crocodylians and birds. Figure 4 Bone texture indicates large zones of large, flat scales and subordinate regions of armor-like skin and cornified epidermis; integumentary sense organs occur on the flat scales that cover the densest regions of neurovascular foramina. The region outside of the crocodylian-like skin is reconstructed with small scales after fossilized skin impressions of tyrannosaurids.

 Illustration: Dino Pulerà.  

Thomas D. Carr, David J. Varricchio, Jayc C. Sedlmayr, Eric M. Roberts and Jason R. Moore. 2017. A New Tyrannosaur with Evidence for Anagenesis and Crocodile-like Facial Sensory System.
 Scientific Reports. 7, 44942 (2017). DOI: 10.1038/srep44942 

[Paleontology • 2014] Qianzhousaurus sinensis • A New Clade of Asian Late Cretaceous long-snouted tyrannosaurids

two individuals of Qianzhousaurus sinensis and a small feathered dinosaur

illustration: Chuang Zhao

The iconic tyrannosaurids were top predators in Asia and North America during the latest Cretaceous, and most species had deep skulls that allowed them to generate extreme bite forces. Two unusual specimens of Alioramus from Mongolia seem to indicate a divergent long-snouted body plan among some derived tyrannosaurids, but the rarity and juvenile nature of these fossils leaves many questions unanswered. Here, we describe a remarkable new species of long-snouted tyrannosaurid from the Maastrichtian of southeastern China, Qianzhousaurus sinensis. Phylogenetic analysis places Qianzhousaurus with both species of Alioramus in a novel longirostrine clade, which was geographically widespread across latest Cretaceous Asia and formed an important component of terrestrial ecosystems during this time. The new specimen is approximately twice the size as both Alioramus individuals, showing that the long-snouted morphology was not a transient juvenile condition of deep-snouted species, but a characteristic of a major tyrannosaurid subgroup.

Junchang Lü, Laiping Yi, Stephen L. Brusatte, Ling Yang, Hua Li & Liu Chen. 2014. A New Clade of Asian Late Cretaceous long-snouted tyrannosaurids. Nature Communications. 5, 3788 doi: dx.doi.org/10.1038/ncomms4788

"Pinocchio Rex" Found; Dinosaur Sported Long Snout

http://news.nationalgeographic.com/news/2014/05/140507-pinocchio-rex-dinosaurs-tyrannosaurus-science-new-species/

[Paleontology • 2014] Nanuqsaurus hoglundi • A Diminutive New Tyrannosaur from the Top of the World

Nanuqsaurus hoglundi Fiorillo & Tykoski 2014
 nearly 2 m. tall at the hips and 7 m. from snout to tail, about half the size of T rex.

Illustration: Karen Carr

Abstract

Tyrannosaurid theropods were dominant terrestrial predators in Asia and western North America during the last of the Cretaceous. The known diversity of the group has dramatically increased in recent years with new finds, but overall understanding of tyrannosaurid ecology and evolution is based almost entirely on fossils from latitudes at or below southern Canada and central Asia. Remains of a new, relatively small tyrannosaurine were recovered from the earliest Late Maastrichtian (70-69Ma) of the Prince Creek Formation on Alaska's North Slope. Cladistic analyses show the material represents a new tyrannosaurine species closely related to the highly derived Tarbosaurus+Tyrannosaurus clade. The new taxon inhabited a seasonally extreme high-latitude continental environment on the northernmost edge of Cretaceous North America. The discovery of the new form provides new insights into tyrannosaurid adaptability, and evolution in an ancient greenhouse Arctic.

Figure 3. Nanuqsaurus hoglundi, holotype, DMNH 21461.
A. Reconstruction of a generalized tyrannosaurine skull, with preserved elements of holotype shown in white. Arrow points to autapomorphic, reduced, first two dentary teeth.
B–E. Photographs and interpretive line drawings of right maxilla piece in medial (B, C); and dorsal (D, E) views. F–I. Photographs and interpretive line drawings of partial skull roof in dorsal (F, G); and rostrolateral (H, I) views. J–M, partial left dentary in lateral (J); medial (K); dorsal (L) views; and close-up of mesial alveoli in dorsal (M) views.

Etymology: Nanuqsaurus, combination of ‘nanuq’ the Iñupiaq word for polar bear and the Greek ‘sauros’ for lizard; hoglundi, named in recognition of Forrest Hoglund for his career in earth sciences and his philanthropic efforts in furthering cultural institutions.

 (Iñupiaq word source: http://alaskool.org/language/diction​aries/inupiaq/dictionary.htm)

Theropod size comparisons, showing the newly discovered Nanuqsaurus hoglundi (A), Tyrannosaurus rex (B and C), Daspletosaurus torosus (D), Albertosaurus sarcophagus (E), Troodon formosus (F), and Troodon sp. (G).

Scale bar equals 1 metre | Doi: 10.1371/journal.pone.0091287

Anthony R. Fiorillo and Ronald S. Tykoski. 2014. A Diminutive New Tyrannosaur from the Top of the World. PLoS ONE. 9 (3): e91287.

 DOI: dx.doi.org/10.1371/journal.pone.0091287

Pygmy tyrannosaur roamed the Arctic

Newly discovered cousin of T rex, Nanuqsaurus hoglundi, inhabited an Arctic island continent around 70m years ago

 http://gu.com/p/3nfdx/tw via @guardian

[Paleontology • 2013] Lythronax argestes | 'King of Gore' | a new tyrannosaurid from the Wahweap formation of southern Utah • Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans

Life Reconstruction of the newly named tyrannosaur Lythronax argestes.

Illustration: Andrey Atuchin

Abstract

The Late Cretaceous (~95–66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah—including a new taxon which represents the geologically oldest member of the clade—to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.

Skull reconstructions and selected cranial elements of Lythronax argestes.

DOI: dx.doi.org/10.1371/journal.pone.0079420

Lythronax argestes

Loewen, Irmis, Sertich, Currie & Sampson 2013

Etymology: Lythronax, from lythron (Greek), gore, and anax (Greek), king; and argestes (Greek), the Homeric wind from the southwest, in reference to the geographic location of the specimen within North America.

Skeletal reconstruction of Lythronax (A) and Teratophoneus (B)Reconstructed skeletons of Lythronax argestes (UMNH VP 20200) and (B) Teratophoneus curriei (UMNH VP 16690), with the respective postcranial material (C-M for Teratophoneus and N-P for Lythronax)

DOI: 10.1371/journal.pone.0079420

Mark A. Loewen,  Randall B. Irmis, Joseph J. W. Sertich, Philip J. Currie and Scott D. Sampson. 2013. Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. PLoS ONE. 8(11): e79420. doi: dx.doi.org/10.1371/journal.pone.0079420

Thomas D. Carr, Thomas E. Williamson, Brooks B. Britt and Ken Stadtman. 2011. Evidence for high taxonomic and morphologic tyrannosauroid diversity in the Late Cretaceous (Late Campanian) of the American Southwest and a new short-skulled tyrannosaurid from the Kaiparowits formation of Utah. Naturwissenschaften 98 (3): 241–246. doi: dx.doi.org/10.1007/s00114-011-0762-7

Lythronax argestes the "King of Gore"

A new species of Tyrannosaur recently uncovered in the badlands of Utah.

 youtube.com/watch?v=gHb5BX4LEis

facebook.com/photo.php?fbid=10151742559931088

http://www.aamulehti.fi/Ulkomaat/1194851083868/artikkeli/utahista+loytyi+uusi+tyrannosauruslaji+sukua+t+rexille+katso+kuvat.html

http://www.ibtimes.co.uk/articles/520097/20131106/king-gore-tyrannosaurus-rex-forefather-lythronax-argestes.htm

Lythronax: a new tyrant and the spread of the tyrannosaurs

A newly named tyrannosaur dinosaur supports the idea that the evolution of these animals was more provincial than previously thought

All hail the Southern King of Gore – Lythronax argestes. As names go in palaeontology that’s a superb entry and one that has more than a nice ring to it. While it is true that new dinosaurs are named all the time, new tyrannosaurs are generally considered rather special since they are not common, and the charisma of the group remains undimmed. Thus the naming of Lythronax in the journal PLOS ONE is unsurprisingly popular, but the animal has way more going for it than a cool name.

http://www.theguardian.com/science/2013/nov/06/lythronax-argestes-tyrannosaurs

[Paleontology / PalaeoIchthyology • 2013] Teleost centrum and jaw elements from the Upper Cretaceous Nemegt Formation (Campanian – Maastrichtian) of Mongolia and a re-identification of the fish centrum found with the theropod Raptorex kreigsteini

RAPTOREX REBUTTAL: A new paper by Newbrey et al 2013 adds even stronger evidence that the small tyrannosaurid skeleton named "Raptorex" was illegally removed from the Late Cretaceous Nemegt Formation of Mongolia, and not from the Early Cretaceous of China (as originally claimed).

http://facebook.com/photo.php?fbid=682305425119461
via Horner Paleo Lab, Museum of the Rockies

Abstract

Isolated centra and a premaxilla of a teleost from the Upper Cretaceous Nemegt Formation (Late Campanian - Early Maastrichtian) of Mongolia are described and aligned with the hiodontids and the Late Cretaceous teleost Coriops from North America. The atlas of the Nemegt taxon has an anterior articular surface with the dorsal half being subdivided into two flat articulator surfaces as in those of the hiodontids. In more posterior abdominal centra, the centrum is strongly constricted at the notochord foramen, the rib loosely articulates in a facet on the lateral wall of the centrum posterior to the parapophysis as in hiodontids, and parapophyses are fused to the centrum. Neural arch articular facets are small and round. Distinct mid-dorsal foramina are absent or small and poorly developed. A single stout premaxilla is relatively straight and has a low rounded dorsal margin on the posterior end. There are two rows of strong conical teeth and the tooth bases of the lateral row protrude laterally. The Nemegt centra are then used to re-identify a teleost centrum associated with the Asian theropod, Raptorex kreigsteini. Initially the fish centrum found with R. kreigsteini was assigned to Lycoptera. The stratigraphic range of Lycopteridae, ~120-135 Ma, was used to infer an age of deposition for the basal taxon Raptorex. Subsequently this centrum was re-identified as a clupeomorph centrum. However, centra of Lycoptera are mainly comprised of the chordacentrum surrounded by a very thin autocentrum, thus giving the appearance of being tubular with an unconstricted notochordal foramen; they are thin-walled, small (≤ 2 mm diameter), and may have a broad bar (presence depends on the species and ontogenetic development) extending the length of the centrum in lateral view. Parapophyses are not fused with the autocentrum and articulate with the centrum at large facets as in those of lower teleosts. Pleural ribs in Lycoptera articulate with the parapophyses. The fish centrum found with R. kreigsteini is of a higher teleost with a well-developed autocentrum strongly constricting the notochord, thereby giving the centrum an amphicoelous shape. This centrum has several aspects in common with the Nemegt Formation teleost centra: poorly developed mid-dorsal foramen; shape and position of the facets, where the arch articulates, being circular and located near the anterior end of the centrum; presence of short, fused parapophyses at the ventro-lateral corner of the centrum; lateral surface of the centrum bearing a series of foramina of small to moderate size that are generally organized into rows. Thus we reject the hypotheses that the fish centrum found with R. kreigsteini has affinities with the Lycopteridae or the Clupeomorpha and reassign the centrum to the hiodontids. The morphological characteristics of the fish centrum found with R. kreigsteini suggest a Late Cretaceous hiodontid-like taxon and thus its co-occurrence with Raptorex suggests that dinosaur is an Upper Cretaceous theropod.

______________________

RAPTOREX REBUTTAL: A new paper by Newbrey et al 2013 adds even stronger evidence that the small tyrannosaurid skeleton named "Raptorex" was illegally removed from the Late Cretaceous Nemegt Formation of Mongolia, and not from the Early Cretaceous of China (as originally claimed). 

The new paper shows that a fossil fish vertebra (backbone) found with the "Raptorex" skeleton does not belong to a "lycopterid" fish, as originally claimed, but instead is indistinguishable from a type of fish only found in the Nemegt Formation of Mongolia. This supports the findings of a previous rebuttal by MOR researchers (Fowler et al., 2011b), which disputed the major claims of the original species description (Sereno et al., 2009).

The findings are important as if "Raptorex" was from the Early Cretaceous (~ 130 million years old, as originally claimed) then it would mean that many of the distinctive features that we associate with tyrannosaurids evolved much earlier in time than previously thought. However, the new paper further supports the view that Raptorex is actually from the late Cretaceous (~ 70 million years ago), and that tyrannosaurs evolved their distinctive features more gradually.

NEWBREY, M.G., BRINKMAN, D.B., WINKLER, D.A., FREEDMAN, E.A., NEUMAN, A.G., FOWLER, D.W., & WOODWARD, H.N. 2013. Teleost centrum and jaw elements from the Upper Cretaceous Nemegt Formation (Campanian – Maastrichtian) of Mongolia and a re-identification of the fish centrum found with the theropod Raptorex kreigsteini. 291-303. in Arratia, Schultze & Wilson (eds), Mesozoic Fishes 5 - Global Diversity and Evolution. Verlag, Munchen, Germany. ISBN 978-3-89937-159-8. http://www.pfeil-verlag.de/07pala/pdf/4_59d11.pdf

[Paleontology • 2010] Cannibalism in Tyrannosaurus rex

Abstract  

Background

Tyrannosaurus rex was one of the largest terrestrial carnivores of all time, and consequently its ecology and diet have been the focus of much discussion. However, there is little direct evidence of diet or feeding habits in this species.

Methodology/Principal Findings

Examination of museum collections has revealed four specimens of Tyrannosaurus rex that bear tooth marks made by large, carnivorous dinosaurs. Because Tyrannosaurus is the only large carnivore known from the Late Maastrichtian of western North America, we infer that Tyrannosaurus made these tooth marks.

Conclusions/Significance

The marks are interpreted as feeding traces and these fossils therefore record instances of cannibalism. Given that this behavior has a low preservation potential, cannibalism seems to have been a surprisingly common behavior in Tyrannosaurus, and this behavior may have been relatively common in carnivorous dinosaurs.

Figure 1. Tooth marks made by Tyrannosaurus rex.

A, hadrosaurid metatarsal (UCMP uncatalogued) and closeup of tooth marks on distal articular surface. 

B, fragment of hadrosaurid pubis (CM 105) showing tooth marks on prepubic process. 

C, ceratopsid? frill element (TMP 1998.102.2) showing tooth mark. 

D, Triceratops right squamosal (YPM 53263) showing tooth marks on edge.

Figure 2. Tyrannosaurus rex bones bearing tooth marks made by Tyrannosaurus rex.

Longrich NR, Horner JR, Erickson GM, Currie PJ (2010) Cannibalism in Tyrannosaurus rex. PLoS ONE 5(10): e13419. doi:10.1371/journal.pone.0013419

T. Rex Was a Cannibal, Bone Gashes Suggest

http://news.nationalgeographic.com/news/2010/10/101015-t-rex-cannibals-paleontology-science/

[Paleontology • 2010] Tyrannosaur Paleobiology: New Research on Ancient Exemplar Organisms

Tyrannosaurs, the group of dinosaurian carnivores that includes Tyrannosaurus rex and its closest relatives, are icons of prehistory. They are also the most intensively studied extinct dinosaurs, and thanks to large sample sizes and an influx of new discoveries, have become ancient exemplar organisms used to study many themes in vertebrate paleontology. A phylogeny that includes recently described species shows that tyrannosaurs originated by the Middle Jurassic but remained mostly small and ecologically marginal until the latest Cretaceous. Anatomical, biomechanical, and histological studies of T. rex and other derived tyrannosaurs show that large tyrannosaurs could not run rapidly, were capable of crushing bite forces, had accelerated growth rates and keen senses, and underwent pronounced changes during ontogeny. The biology and evolutionary history of tyrannosaurs provide a foundation for comparison with other dinosaurs and living organisms.

Stephen L. Brusatte, Mark A. Norell, Thomas D. Carr, Gregory M. Erickson, John R. Hutchinson, Amy M. Balanoff, Gabe S. Bever, Jonah N. Choiniere, Peter J. Makovicky, and Xing Xu. Tyrannosaur Paleobiology: New Research on Ancient Exemplar Organisms. Science, 2010; 329 (5998): 1481-1485 DOI: 10.1126/science.1193304

Tyrannosaurus redux: T. rex was more than just a large carnivore at top of food chain, new findings reveal: http://www.sciencedaily.com/releases/2010/09/100916145131.htm

[Paleontology • 2009] Raptorex kriegsteini • Tyrannosaurid skeletal design first evolved at small body size

Fig. 1: Skull, endocast, and premaxillary teeth of the Early Cretaceous tyrannosauroid R. kriegsteini. 

Nearly all of the large-bodied predators (>2.5 tons) on northern continents during the Late Cretaceous were tyrannosaurid dinosaurs. We show that their most conspicuous functional specializations—a proportionately large skull, incisiform premaxillary teeth, expanded jaw-closing musculature, diminutive forelimbs, and hindlimbs with cursorial proportions—were present in a new, small-bodied, basal tyrannosauroid from Lower Cretaceous rocks in northeastern China. These specializations, which were later scaled up in Late Cretaceous tyrannosaurids with body masses approaching 100 times greater, drove the most dominant radiation of macropredators of the Mesozoic.

Fig. 2: Postcranial features of the Early Cretaceous tyrannosauroid R. kriegsteini.

Fig. 4: Temporal, geographic, and phylogenetic patterns among tyrannosauroids. 

(A) Temporally calibrated phylogeny of tyrannosauroids based on phylogenetic analysis, showing an early diversity of basal tyrannosauroids (shaded) from localities across Laurasia and plotted on an Early Cretaceous paleogeographic map. Proceratosaurus and Xiongguanlong were excluded from this plot because of limited available morphologic data and age uncertainty, respectively. 

(B) Phylogram scaled to the amount of character change (delayed transformation) 

Circled nodes 1 to 3 outline major transformations in tyrannosauroid evolution. Taxonomic definitions of Tyrannosauroidea, Tyrannosauridae, and other taxa follow. 

Abbreviations for biogeographic area and localities: A, Asia; E, Europe; NA, North America; 

1, Stokesosaurus; 2, Proceratosaurus and Eotyrannus; 3, Aviatyrannis; 4, Guanlong; 5, Dilong; 6, Xiongguanlong; 7, Raptorex.

Sereno, P.; Tan, L.; Brusatte, S. L.; Kriegstein, H. J.; Zhao, X. & Cloward, K. (2009). "Tyrannosaurid skeletal design first evolved at small body size". Science. 326 (5951): 418–422. doi:10.1126/science.1177428

http://www.sciencemag.org/content/326/5951/418.figures-only

http://scienceblogs.com/notrocketscience/2009/09/raptorex_tiny_king_of_thieves_shows_how_tyrannosaurus_body_p.php

http://blogs.discovermagazine.com/80beats/2010/09/17/how-tyrannosaurs-grew-from-tiny-jackals-to-ferocious-giants/

[Paleontology • 2011] Reanalysis of “Raptorex kriegsteini”: A Juvenile Tyrannosaurid Dinosaur from Mongolia

The carnivorous Tyrannosauridae are among the most iconic dinosaurs: typified by large body size, tiny forelimbs, and massive robust skulls with laterally thickened teeth. The recently described small-bodied tyrannosaurid Raptorex kreigsteini is exceptional as its discovery proposes that many of the distinctive anatomical traits of derived tyrannosaurids were acquired in the Early Cretaceous, before the evolution of large body size. This inference depends on two core interpretations: that the holotype (LH PV18) derives from the Lower Cretaceous of China, and that despite its small size, it is a subadult or young adult. Here we show that the published data is equivocal regarding stratigraphic position and that ontogenetic reanalysis shows there is no reason to conclude that LH PV18 has reached this level of maturity. The probable juvenile status of LH PV18 makes its use as a holotype unreliable, since diagnostic features of Raptorex may be symptomatic of its immature status, rather than its actual phylogenetic position. These findings are consistent with the original sale description of LH PV18 as a juvenile Tarbosaurus from the Upper Cretaceous of Mongolia. Consequently, we suggest that there is currently no evidence to support the conclusion that tyrannosaurid skeletal design first evolved in the Early Cretaceous at small body size.

Fowler DW, Woodward HN, Freedman EA, Larson PL, Horner JR (2011) Reanalysis of “Raptorex kriegsteini”: A Juvenile Tyrannosaurid Dinosaur from Mongolia. PLoS ONE. 6(6): e21376. doi:10.1371/journal.pone.0021376

Fig. 1: Skull, endocast, and premaxillary teeth of the Early Cretaceous tyrannosauroid R. kriegsteini. 

Nearly all of the large-bodied predators (>2.5 tons) on northern continents during the Late Cretaceous were tyrannosaurid dinosaurs. We show that their most conspicuous functional specializations—a proportionately large skull, incisiform premaxillary teeth, expanded jaw-closing musculature, diminutive forelimbs, and hindlimbs with cursorial proportions—were present in a new, small-bodied, basal tyrannosauroid from Lower Cretaceous rocks in northeastern China. These specializations, which were later scaled up in Late Cretaceous tyrannosaurids with body masses approaching 100 times greater, drove the most dominant radiation of macropredators of the Mesozoic.

Fig. 2: Postcranial features of the Early Cretaceous tyrannosauroid R. kriegsteini.

Fig. 4: Temporal, geographic, and phylogenetic patterns among tyrannosauroids. 

(A) Temporally calibrated phylogeny of tyrannosauroids based on phylogenetic analysis, showing an early diversity of basal tyrannosauroids (shaded) from localities across Laurasia and plotted on an Early Cretaceous paleogeographic map. Proceratosaurus and Xiongguanlong were excluded from this plot because of limited available morphologic data and age uncertainty, respectively. 

(B) Phylogram scaled to the amount of character change (delayed transformation) 

Circled nodes 1 to 3 outline major transformations in tyrannosauroid evolution. Taxonomic definitions of Tyrannosauroidea, Tyrannosauridae, and other taxa follow. 

Abbreviations for biogeographic area and localities: A, Asia; E, Europe; NA, North America; 

1, Stokesosaurus; 2, Proceratosaurus and Eotyrannus; 3, Aviatyrannis; 4, Guanlong; 5, Dilong; 6, Xiongguanlong; 7, Raptorex.

Sereno, P.; Tan, L.; Brusatte, S. L.; Kriegstein, H. J.; Zhao, X. & Cloward, K. (2009). "Tyrannosaurid skeletal design first evolved at small body size". Science. 326 (5951): 418–422. doi:10.1126/science.1177428

http://www.sciencemag.org/content/326/5951/418.figures-only

http://scienceblogs.com/notrocketscience/2009/09/raptorex_tiny_king_of_thieves_shows_how_tyrannosaurus_body_p.php

http://blogs.discovermagazine.com/80beats/2010/09/17/how-tyrannosaurs-grew-from-tiny-jackals-to-ferocious-giants/

Tyrannosaur Paleobiology: New Research on Ancient Exemplar Organisms

http://www.sciencemag.org/content/329/5998/1481.abstract

[Paleontology • 2010] Family Proceratosauridae: [a coelurosaur, a tyrannosauroid] • hylogenetic position of the theropod dinosaur Proceratosaurus bradleyi from the Middle Jurassic of England

Figure 1. Proceratosaurus bradleyi, type skull: NHM R 4860.

The cranial osteology of the small theropod dinosaur Proceratosaurus from the Bathonian of Minchinhampton, England, is described in detail, based on new preparation and computed tomography (CT) scan images of the type, and only known, specimen. Proceratosaurus is an unusual theropod with markedly enlarged external nares and a cranial crest starting at the premaxillary–nasal junction. The skull is highly pneumatic, with pneumatized nasals, jugals, and maxillae, as well as a highly pneumatic braincase, featuring basisphenoid, anterior tympanic, basipterygoid, and carotid recesses. The dentition is unusual, with small premaxillary teeth and much larger lateral teeth, with a pronounced size difference of the serrations between the mesial and distal carina. The first dentary tooth is somewhat procumbent and flexed anteriorly. Phylogenetic analysis places Proceratosaurus in the Tyrannosauroidea, in a monophyletic clade Proceratosauridae, together with the Oxfordian Chinese taxon Guanlong. The Bathonian age of Proceratosaurus extends the origin of all clades of basal coelurosaurs back into the Middle Jurassic, and provides evidence for an early, Laurasia-wide, dispersal of the Tyrannosauroidea during the late Middle to Late Jurassic.

Keywords: Bathonian; biogeography; Coelurosauria; phylogeny; Proceratosauridae; Tyrannosauroidea

Figure 2. Proceratosaurus bradleyi, type skull: NHM R 4860. Stereophotographs

Figure 24. Stratigraphic distribution and ghost lineages in basal coelurosaurs, especially tyrannosauroids.

Figure 26. Biogeographic distribution of Jurassic tyrannosauroids. 

1, Proceratosaurus bradleyi, Great Oolite, England (Bathonian); Stokesosaurus langhami, Kimmeridge Clay, England (Tithonian); 2, Guanlong wucaii, Shishougou Formation, Xinjiang, China (Oxfordian); 3, Aviatyrannis jurassica, Guimarota Beds, Portugal (Kimmeridgian); 4, Stokesosaurus clevelandi, Morrison Formation, Utah, USA (Kimmeridgian–Tithonian).

Rauhut, O.W.M., Milner, A.C. and Moore-Fay, S. (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. doi: 10.1111/j.1096-3642.2009.00591.x

Brusatte, S.L.; Norell, M.A.; Carr, T.D.; Erickson, G.M.; Hutchinson, J.R.; Balanoff, A.M.; Bever, G.S.; Choiniere, J.N.; Makovicky, P.J.; and Xu, X. (2010). "Tyrannosaur paleobiology: new research on ancient exemplar organisms". Science 329: 1481−1485. doi: 10.1126/science.1193304

https://sites.google.com/site/Brusatte/

[Palaeontology • 2011] Zhuchengtyrannus magnus • A new, large tyrannosaurine theropod from the Upper Cretaceous of China

Zhuchengtyrannus magnus 

[Late Cretaceous, 70 Ma]

Abstract

Tyrannosaurids are primarily gigantic, predatory theropod dinosaurs of the Cretaceous. Here we report a new member of the tyrannosaurid clade Tyrannosaurinae from the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China, based on a maxilla and associated dentary. The discovery of this animal, here named Zhuchengtyrannus magnus gen. et sp. nov., adds to the known diversity of tyrannosaurids in Asia. Z. magnus can be identified by a horizontal shelf on the lateral surface of the base of the ascending process, and a rounded notch in the anterior margin of the maxillary fenestra. Several additional features contribute to a unique combination of character states that serves to further distinguish Z. magnus from other taxa. Comparisons with other tyrannosaurids suggest that Zhuchengtyrannus was a very large theropod, comparable in size to both Tarbosaurus and Tyrannosaurus.

Highlights

► A new tyrannosaurine theropod, Zhuchengtyrannus magnus is named based on a maxilla and dentary. ► This is a large animal, equivalent in size to Tyrannosaurus and Tarbosaurus. ► This is from the Late Cretaceous of eastern China.

Keywords: Dinosaur; Saurischian; Tyrannosaurid; Skull; China; Cretaceous

David W. E. Hone, Kebai Wang, Corwin Sullivan, Xijin Zhao, Shuqing Chen, Dunjin Li, Shuan Ji, Qiang Ji and Xing Xu. 2011. A new, large tyrannosaurine theropod from the Upper Cretaceous of China. Cretaceous Research. 32 (4): 495–503. http://dx.doi.org/10.1016/j.cretres.2011.03.005

A New Giant Tyrant, Zhuchengtyrannus http://t.co/CMZyzJF via @SmithsonianMag

Zhuchengtyrannus magnus, T-Rex's gigantic cousin, discovered in China (Wired UK) http://t.co/vi9ijQR