Daspletosaurus horneri: a new species of Tyrannosaurid Dinosaur from the Late Cretaceous of Montana.

Tyrannosaurs are possibly the most iconic of all Dinosaurs, appearing in almost all Dinosaur-related fiction and among the most popular exhibits in museums of palaeontology. They were large, bipedal carnivorous Therapods from the Late Cretaceous of North America and Asia, noted for their reduced forearms and (in fictional accounts) presumed ferocity. Tyrannosaur remains are quite numerous in some North American deposits, and the group has been extensively studied, though these studies have concentrated largely on the diet and locomotion of the animals, with other areas of their biology often neglected.

In a paper published in the journal Scientific Reports on 30 March 2017, Thomas Carr of Carthage College, David Varricchio of the Department of Earth Sciences at Montana State University, Jayc Sedlmayr of the Louisiana State University Health Sciences Centre, Eric Roberts of Geosciences at James Cook University and Jason Moore of Honors College at the University of New Mexico describe a new species of Tyrannosaurid Dinosaur from the Late Cretaceous Two Medicine Formation of Glacier, Lewis and Clark and Teton counties in Montana.

The new species is placed in the genus Daspletosaurus, as it is thought to be closely related to the only previously described species in this genus, Daspletosaurus torosus, and given the specific name horneri, in honour of the distinguished American palaeontologist Jack Horner, for his extensive work on the Two Medicine Formation and mentoring of many students who went on to become leaders in the field. The species is described from a complete skull, partial pectoral limb, and nearly complete hind limb, thought to come from one animal, with several other specimens referred, including an incomplete skull, partial axial series, and partial pelvic girdle and hind limb, a nearly complete dentary of a small juvenile, a maxilla, partial postorbital, and parietal, a partial mandibular ramus, a left ectopterygoid and a right ectopterygoid. 

Skull and jaws of Daspletosaurus horneri; (A) photograph and, (B) labeled line drawing of skull and jaws in left lateral view; (C) photograph and, (D) labelled line drawing of occiput and suspensorium in caudal view; (E) photograph and, (F) labelled line drawing of skull in dorsal view. Scale bars equal 10 cm. Carr et al. (2017).

The largest specimen of Daspletosaurus horneri is estimated to have been 9 m in length and 2.2 m at the acetabulum (hip joint). The species has a distinctly wide dental arcade at the front of the snout compared to other Tyrannosaurids, and shows a reduction in tooth numbers in the oldest specimens, something that has been recorded in some other Tyrannosaurids, including Daspletosaurus torosus and Tyranosaurus rex (Tyrannosaurs, unlike Mammals, continuously shed and grew new teeth throughout their lives, so that the number and positioning of teeth was not fixed; this meant that as the animals grew and their jaws got longer the number of teeth tended to increase, but in some species, including Daspletosaurus horneri, the adults have a slightly reduced tooth count compared to the oldest subadults).

 The growth series of Daspletosaurus horneri, 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. Carr et al. (2017).

Several of the specimens referred to the species show exceptional preservation of the facial bones (premaxilla, maxilla, nasal, lacrimal, jugal, postorbital, squamosal, dentary), enabling Carr et al. to make an assessment of the soft tissue covering of the face. These specimens show a course, hummocky texture to the surface of these bones, similar to that seen in extant Crocodylians, which is assumed to be indicative of a scaly outer integument (skin) like that of Crocodylians.

Also preserved are the neurovascular foramina, channels in the bone through which nerves and blood vessels run. In modern Birds these are limited to the jaw tips, the caudal end of the maxilla, and in a row along the side of the lower jaw, but in Crocodylians they are arranged in repeated rows associated with the positioning of scales; this is also the pattern seen in Daspletosaurus horneri, lending further support to the idea that these animals had a face covered by a Crocodile-like scaly skin.

These neurovascular foramina are very numerous and densely packed, which is taken to be indicative of a highly sensitive snout. This is also seen in modern Crocodylians, where the facial skin plays an important role in a number of behaviours, most notably detecting movements in water that could indicate potential prey, and monitoring the temperature of nesting sites (very important for Crocodylians, which have a temperature dependent method of sex determination). Tyrannosaurids are thought to have been terrestrial hunters, making it highly unlikely that they would have used sensitive facial skin to detect movements in the water, and though Carr et al, consider it quite likely that they had a temperature dependent sex determination system and a consequent need to asses the temperature of nesting sites, they feel that this in itself would be unlikely to be the sole reason for the high levels of  neurovascular development in the face of Daspletosaurus horneri. Instead they suggest that this area of skin may have been important in tactile communication, possibly with Tyrannosaurs touching or rubbing one another's faces during courtship.

The craniofacial epidermis of Daspletosaurus horneri, based on comparison with its closest living relatives, Crocodylians and Birds. 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. Dino Pulerà in Carr et al. (2017).

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A new species of Mamenchisaurid Sauropod from the Late Jurassic of Chongqing.

The Mamenchisaurids are a unique group of Sauropods found only in Asia, and thought to be indicative of the isolation of that continent during much of the Jurassic. They arose of a more diverse Sauropd fauna in the Middle Jurassic, and are the only group present in the Late Jurassic, being replaced by Titanosaurs in the Early Cretaceous. However well preserved Sauropod skeletons from the Late Jurassic of Asia are rare, with all known Sauropod specimens being assigned to a single genus, Mamenchisaurus, making it unclear if there was a wider diversity of Sauropods not recorded in the fossil record, a low diversity population genuinely all belonging to a small number of closely related species, or a wider range of Sauropods erroneously assigned to a single group.

In a paper published in the Journal of Vertebrate Paleontology on 26 January 2015, a group of scientists led by Lida Xing of the School of the Earth Sciences and Resources at the China University of Geosciences, describe a new species of Mamenchisaurid from the Late Jurassic Suining Formation in the Qijiang Petrified Wood and Dinosaur Footprint National Geological Park in Chongqing Municipality in South China.

The new species is named Qijianglong guokr, where ‘Qijianglong’ means ‘Qijiang-dragon’ and ‘guokr’ means ‘nutshell’, honouring the Guokr Science Social Network for their support of palaeontology in Qijiang. The specimen comprises the skull roof, the braincase, the right pterygoid, fragments of the right antorbital elements, the right postorbital and right quadrate; a complete cervical series, the thoracic dorsal series and the distal caudal series, numerous fragments of neural arches, numerous rib fragments; numerous hemal arch fragments, the left pubis and a pedal phalanx.

Caudal series of Qijianglong guokr. A mid-caudal vertebra in (A) anterior view; (B) left lateral view; (C) posterior view. Distal caudal series in left lateral view: (D) possible caudal vertebrae 15–20; (E) possible caudal vertebrae 21–26; (F) possible caudal vertebrae 27–39; (G) close-up photograph of possible caudal vertebrae 35–41; (H) close-up photograph of possible caudal vertebrae 40 and 41. The centrum of the caudal vertebra 41 is fused to that of the caudal vertebra 40. Arrow with number indicates a character diagnostic to this taxon. Xing et al. (2015).

While Qijianglong guokr is clearly a Mamenchisaurid it is distinctive enough to merit its placement in a separate genus, indicating that this group were indeed more diverse in the Late Jurassic. It also shows a number of features that indicate the group spit off quite early in the history of the Sauropods as a whole, and underwent considerable convergent evolution with other large members of the group. Xing et al.  suggest that a more comprehensive review of the group might be usefull.

See also…

A Mamenchisaurid Sauropod Dinosaur from Thailand.

The Mamenchisaurids are a group of Sauropod dinosaurs known from the Late Jurassic and Early Cretaceous of China. Their taxonomy is not well understood, but they are distinctive in a number of ways from Sauropods in other parts of the world, which (along with studies on other groups) is taken as evidence that China was separated from other land-masses during this time.

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The nearly complete skeleton of two gigantic Titanosaurs from Southern Patagonia, Argentina.

Titanosaurs were a group of Sauropod Dinosaurs that became the predominant large herbivores during the last 30 million years of the Cretaceous. They were a diverse group, and included several truly gigantic species, which are thought to have been the largest terrestrial animals ever to have lived. Unfortunately most of these gigantic species are known only from fragmentary remains, and we know relatively little about their biology or evolution (we know they were bigger than everything else, but not how big they actually got, nor do we know if gigantic Titanosaurs were a distinct evolutionary lineage, or if gigantism arose separately several times within the group).

In a paper published in the journal Nature Scientific Reports on 4 September 2014, a team of scientists led by Kenneth Lacovara of the Department of Biodiversity, Earth and Environmental Science at Drexel University describe the almost complete skeleton of two gigantic Titanosaurs from south-western Patagonia, Argentina.

The new specimens are determined to be distinct from any previously described Titanosaur, and placed in a new species, named Dreadnoughtus schrani, where ‘Dreadnoughtus’ derives from the Old English ‘dreadnought’ meaning ‘fearless’ and also alludes to the class of large battleships used in the early twentieth century, and ‘schrani’ honours the American entrepreneur Adam Schran, for his support of the research. 

Axial skeletal anatomy of the gigantic Titanosaur Dreadnoughtus schrani. Posterior (~9th) cervical vertebra in (A) left lateral, (B) right lateral, (C) posterior, and (D) ventral views. (E) Anterior (~4th) dorsal vertebra in right lateral view. Middle (~6th) dorsal vertebra in (F) left lateral and (G) anterior views. (H) Posterior (~7th) dorsal vertebra in right lateral view. Posterior (~8th) dorsal vertebra in (I) left lateral and (J) posterior views. (K) Partial sacrum in ventral view. (L) Biconvex first caudal vertebra in posterior view. (M) First 32 caudal vertebrae and 18 haemal arches in left lateral view (positions of first 21 caudal vertebrae and haemal arches 4 to 18 known with certainty).  Abbreviations: acpl, anterior centroparapophyseal lamina; apcdl, accessory posterior centrodiapophyseal lamina; a-spdl, anterior ramus of spinodiapophyseal lamina; cdf, centrodiapophyseal fossa; cpol, centropostzygapophyseal lamina; dp, diapophysis; nc, neural canal; ns, neural spine; pacdf, parapophyseal centrodiapophyseal fossa; pcdl, posterior centrodiapophyseal lamina; pcdl-f posterior centrodiapophyseal fossa, pcpl, posterior centroparapophyseal lamina; pe, paddle-shaped distal expansion; pocdf, postzygapophyseal centrodiapophyseal fossa; podl, postzygodiapophyseal lamina; posdf, postzygapophyseal spinodiapophyseal fossa; poz, postzygapophysis; pp, parapophysis; ppdl, paradiapophyseal lamina; prdl, prezygodiapophyseal lamina; prsdf, prezygapophyseal spinodiapophyseal fossa; prsl, prespinal lamina; prz, prezygapophysis; p-spdl, posterior ramus of spinodiapophyseal lamina; s6, sixth sacral vertebra; sdf, spinodiapophyseal fossa; spdl, spinodiapophyseal lamina; spof, spinopostzygapophyseal fossa; spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina; sr, sacral rib; sy, sacricostal yoke; tp, transverse process; tpol, intrapostzygapophyseal lamina; tprl, intraprezygapophyseal lamina. Scale bars equal 50 cm. Lacovara et al. (2014).

Dreadnoughtus schrani is thought to have been one of the largest Titanosaurs (though it is not claimed that it was the largest species), and is sufficiently complete that it is possible to estimate its size when alive. The larger specimen is thought to have been about 26 m in length, and to have weighed about 59.3 tons; this compares to an estimated 35 tons for the largest known Brachiosaurid Sauropod, Giraffatitan, and 14.8 tons for the largest Diplodocid Sauropod, Diplodocus, although considerable smaller than the 170 tons reached by living Blue Whales. It was also possible to study the histology (cell structure) of several bones, which strongly suggests that this specimen was still growing at the time when it died.

Reconstruction, appendicular skeletal anatomy, and bone histology of Dreadnoughtus schrani. (A) Reconstructed skeleton and body silhouette in left lateral view with preserved elements in white. (B) Left scapula and coracoid in lateral view. (C) Sternal plates in ventral view. (D) Left forelimb (metacarpus reconstructed) in anterior view. (E) Left pelvis (ilium partially reconstructed) in lateral view. (F) Left hind limb in anterior view (metatarsus and pes partially reconstructed and reversed from right). (G) Transverse ground thin section of humeral shaft, showing heavy secondary remodelling (arrow indicates extent of dense osteon formation), a thick layer of well-vascularized fibrolamellar bone, and a lack of lines of arrested growth or an external fundamental system. Abbreviations: acet, acetabulum; acf, acromial fossa; acp, acromial process; acr, acromial ridge; ast, astragalus; cc, cnemial crest; cof, coracoid foramen; cor, coracoid; dpc, deltopectoral crest; fem, femur; fhd, femoral head; fib, fibula; flb, fibrolamellar bone; gl, glenoid; hum, humerus; il, ilium; ilp, iliac peduncle; isc, ischium; isp, ischial peduncle; lt, lateral trochanter; mtI, metatarsal I; mtII, metatarsal II; of, obturator foramen; pop, postacetabular process; prp, preacetabular process; pu, pedal ungual; pub, pubis; pup, pubic peduncle; rac, radial condyle; rad, radius; sc, scapula; scb, scapular blade; sr, secondary remodelling; tib, tibia; tpp, tuberosity on preacetabular process; ul, ulna; ulc, ulnar condyle. Scale bars equal 1 m in (A) to (F) and 1 mm in (G). Lacovara et al. (2014).

See also…

 A new species of Titanosaur from the Late Cretaceous of northwestern Madagascar.

Titanosaurs were the dominant group of Sauropod Dinosaurs in many Late Cretaceous faunas. The group included the very largest Sauropods, and therefore also the very largest known land animals of any type. Titanosaur remains were first found in Madagascar in the 1890s, though the first species from Madagascar...

 A new species of Titanosaur from the Early Cretaceous of northern Texas.

Sauropod dinosaurs were massive, long-necked, long-tailed creatures that have long been regarded as the largest land animals ever to have lived. They reached...

 Dwarf Titanosaur eggs from the Haţeg Basin in Romania.

During the later part of the Cretaceous global sea levels were...

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Reconstructing the Paluxy River Dinosaur Chase Sequence.

In 1940 palaeontologist Roland Bird of the American Museum of Natural History in New York described and partially excavated a sequence of Dinosaur footprints along the Paluxy River at Glen Rose in Texas. In the intervening time this sequence has become one of the best known Dinosaur trackways in the world, most notably a chase sequence which apparently showed a Theropod Dinosaur in pursuit of a Sauropod, which for many years became a standard inclusion in popular books on Dinosaurs.

Since Bird’s excavation much of the site has been destroyed by the actions of the Paluxy River (constant flooding was a problem during Bird’s excavations). The portions excavated by Bird were split in two, with some blocks going to the American Museum of Natural History and some to the Texas Memorial Museum. Unfortunately it was discovered in 1988 that the specimens at the Texas Memorial Museum had begun to deteriorate, deterioration which has continued to date despite attempts at preservation.

In a paper published in the journal PLoS One on 2 April 2014, Peter Falkingham of the Structure and Motion Laboratory at the Department of Comparative Biomedical Sciences at the Royal Veterinary College in London and the Department of Ecology and Evolutionary Biology at Brown University, Karl Bates of the Department of Musculoskeletal Biology II at the Institute of Ageing and Chronic Disease at the University of Liverpool and James Farlow of the Department of Geosciences at Indiana-Purdue University, describe the reconstruction of a three dimensional model of the Paluxy River Dinosaur Chase Sequence, using Bird’s original photographs and maps of the site, and LiDAR laser scans of the surviving material in the American Museum of Natural History and Texas Memorial Museum.

Sixteen of Bird’s original photographs used in the photogrammetric reconstruction of the trackway. Note that the state of excavation (flooded parallel trackways, sandbags, tools etc) varies between images, causing complications for the reconstruction. Falkingham et al. (2014).

The photographic methods available to Bird in 1940 were not comparable to modern techniques, nor are the focal lengths or even models of camera used by Bird known. Nevertheless Bird appreciated the value of photography as a recording technique at a palaeontolological excavation, and took a large number of pictures, seventeen of which were used in Falkingham et al.’s reconstruction. Unfortunately these pictures were mostly taken facing towards the south, limiting the amount of three dimensional reconstruction possible from them, and in addition they are of variable quality, and contain numerous unwanted items, such as people, tools, areas of flooding and sandbags used to contain said flooding.

Bird also made numerous maps and drawings of the site, using lengths of string to obtain accurate measurements despite encroaching flooding. Comparison of these maps to the photographs suggests that they were extremely accurate, although they differed in the extent to which the tracks curved.

R.T. Bird’s maps of the Paluxy ‘chase sequence.’ (a) Bird’s Rye chart, (b) the Austin chart, and (c) the Austin and Rye charts overlaid. Note that the Austin and Rye charts diverge toward the north. Falkingham et al. (2014).

Falkingham et al. created a three dimensional model using scanned photographs plus data from the LiDAR scans of the surviving blocks. This reconstruction was compared to the maps produced by Bird, which, although apparently accurate in their spacings, differed in the curvature of the trackways. Using these methods they were able to reconstruct 45 m of trackway, concluding from the photographic evidence that the more curved interpretation of the tracks was the more accurate. The resolution of the images was improved by using height-based colouration, revealing extra Theropod tracks in the LiDAR scanned blocks that had not been detected by Bird at the time of reconstruction.

Photogrammetric reconstruction of Bird’s chase sequence. Far left, photo-textured and height mapped plan-view of the reconstructed trackway. Right, photo-textured and height mapped views, top to bottom; isometric view along trackway, close up of high fidelity southern end, close up of poor quality northern end. Falkingham et al. (2014).

See also...

 Avian footprints from the Early Cretaceous of Victoria State, Australia.

 Early Cretaceous Dinosaur footprints from Sichuan Province, China.

 Elephant trackways from the United Arab Emirates.

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A Sauropod Dinosaur from the Middle Jurassic of Yunnan Province, China.

Sauropod dinosaurs were massive, long-necked, long-tailed creatures that have long been regarded as the largest land animals ever to have lived. They reached their most diverse in the Late Jurassic, with only two groups surviving into the Cretaceous, and only one of those groups and only one of those groups surviving till the end of the period. 

In a forthcoming paper in the journal Acta Palaeontologica Polonica, available online since 6 June 2013, Lida Xing of the School of the Earth Sciences and Resources at the China University of Geosciences, Tetsuto Miyashita and Philip Currie of the Department of Biological Sciences at the University of Alberta, Hailu You of the Institute of Geology at the Chinese Academy of Geological Sciences and Zhiming Dong of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, describe a new species of Sauropod Dinosaur from the lower Middle Jurassic Zhanghe Formation near Xiabanjing in Yuanmou County of Yunnan Province, China.

The new species is named Nebulasaurus taito, where 'Nebulasaurus' means 'misty-cloud-lizard', a reference to Yunnan province where the specimen was found ('Yunnan' means 'southern cloudy' in Chinese) and 'taito' honours the Taito Corporation of Japan, who funded the field project during which the specimen was found. The species is described from an isolated brain-case.

Photographs of Nebulasaurus. (A) The braincase in right lateral view. (B) Details of the metotic region in left lateral view. Abbreviations: fo, fenestra ovalis, jf, jugular foramen, XII, foramen for hypoglossal nerve. Xing et al. (2013).

See also...

 A new species of Titanosaur from the Early Cretaceous of northern Texas.

 A new species of Diplodocid Dinosaur from the Late Jurassic of northern Wyoming.

 Dwarf Titanosaur eggs from the Haţeg Basin in Romania.

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Dinosaur remains from northwestern Saudi Arabia.

Dinosaurs are the most distinctive element of Mesozoic Vertebrate faunas, arising in the Triassic, and coming to dominate all known terrestrial ecosystems during the Jurassic and Cretaceous, before disappearing abruptly (other than the still extant Birds) at the end of that period. Despite this widespread distribution, very few Dinosaur remains are known from the Middle East, with a few scattered remains recorded from Oman, Jordan, Yemen, Egypt and Lebanon, and, to date, only two recorded Dinosaur finds from Saudi Arabia, and unidentified Sauropod, possibly a Titanosaur, and some other unidentified bones, all from the late Cretaceous Adaffa Formation of the Midyan Peninsula, in the northwest of the country, collected between 2004 and 2008 by a joint expedition of the Saudi Geological Survey and the Egyptian Geological Museum.

In a paper published in the journal PLoS One on 26 December 2013, a team of scientists led by Benjamin Kear of the Department of Earth Sciences at Uppsala University formerly describe these Dinosaur  specimens for the first time.

Geological map of northeast of Saudi Arabia, showing outcrops of the Addafa Formation. Kear et al. (2014).


The material comprises seven caudal (tail) vertebrae, plus two other fragments, from a Sauropod Dinosaur, plus two Theropod teeth, collected from a limestone outcrop 11 km northeast of Al Kuraybah. The specimens were disarticulated, apparently due to water turbulence, but are thought to come from only two animals (i.e. one Sauropod and one Theropod). The most complete vertebra has a length of 105 mm and a height of 133 mm, and does indeed appear to be from a Titanosaur. Both of the teeth are fragmentary in nature, though they are distinctively Theropod in nature, flattened with a serrated cutting edge, and are thought to most likely be from an  Abelisaurid.

Dinosaur remains from the Adaffa Formation of Saudi Arabia. Titanosaurian distal caudal vertebra in: (A) anterior; (B) lateral; and (C) posterior views. Abelisaurid teeth including: (D) crown fragment with enlargement of the distal denticles; and maxillarydentary tooth shown in distal (E) and lateral (F) views with enlargements of the distal carina and baso-apical enamel ridges. Kear et al. (2014)

See also A dwarf Tyrannosaurid from the Late Cretaceous of northern Alaska, Bite marks on the bones of Late Cretaceous juvenile Ornithischian Dinosaurs from Utah, A new species of Theropod Dinosaur from the Late Jurassic of Portugal, A new species of Titanosaur from the Early Cretaceous of Texas and The foot of a small Alvarezsauroid Dinosaur from Inner Mongolia, China.

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A new species of Theropod Dinosaur from the Late Jurassic of Portugal.

The Late Jurassic Megalosaurid Theropod Dinosaur Torvosaurus tanneri was first discovered in Colorado in 1971, with a number of specimens were discovered during the 1970s. In 2000 fragmentary material was discovered in Late Jurassic deposits in central Portugal, with a number of subsequent specimens being found in the area and assigned to the species.

However in a paper published in the Journal of Systematic Palaeontology in 2007, Mathew Carrano of the Department of Paleobiology at the National Museum of Natural History, Roger Benson, then of the Department of Earth Sciences at the University of Cambridge and Scott Sampson of the Natural History Museum of Utah and Department of Geology and Geophysics at the University of Utah challenged the assignation of the Portuguese material to Torvosaurus tanneri, sugesting that while the material could probably assigned to the genus, it was not sufficient to assign it to species level.

In a paper published in the journal PLoS One on 5 March 2014, Christophe Hendrickx and Octávio Mateus of the Departamento de Ciencias de terra at the Universidade Nova de Lisboa and the Museu de Lourinha formerly describe the Portuguese material as a new species, Torvosaurus guyneyi.

Reconstruction of Torvosaurus guyneyi in lateral view. (A) Skeletal reconstruction illustrating, in red, the elements present in the holotype specimen and, in blue, the elements tentatively assigned to this species (B) Skull reconstruction illustrating the incomplete left maxilla. Scale bars are (A) 1 m, and (B) 10 cm. Hendrickx & Mateus (2014).

See also The foot of a samll Alvarezauroid Dinosaur from Inner Mongolia, China, A new species of Abelisauroid Dinosaur from the Late Cretaceous of Madagascar, A basal Tetanuran Dinosaur tooth from the Late Jurassic of the Czech Republic, An Abelisauroid Dinosaur from the Late Cretaceous of Brazil and Dental pathology in a Jurassic Theropod Dinosaur.

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