Siamraptor suwati: A new species of Allosauroid Dinosaur from the Early Cretaceous of Thailand.

The Tetanurans are a large subgroup of the Theropod Dinosaurs, including the Spinosaurs, Tyranosaurs, Ornithomimids, Maniraptors, Therizinosaurs, Oviraptors, Birds, Troodontids, Dromeosaurs, Allosaurs, Raptors and other groups. They appeared in the Middle Jurassic and different groups have flourished ever since, though only one group, the Birds, survived the end-Cretaceous extinction. The first of these groups to come to prominence were the Allosauroids and Megalosauroids, groups which began to produce large-bodied species in the Middle Jurassic, and dominated the top-predator roles in most terrestrial ecosystems until the early Late Cretaceous.

In a paper published in the journal PLoS One on 9 October 2019, Duangsuda Chokchaloemwong of the Northeastern Research Institute of Petrified Wood and Mineral Resources at Nakhon Ratchasima Rajabhat University, Soki Hattori of the Institute of Dinosaur Research at Fukui Prefectural University, and the Fukui Prefectural Dinosaur Museum, Elena Cuesta, also of the Institute of Dinosaur Research at Fukui Prefectural University, Pratueng Jintasakul, also of the Northeastern Research Institute of Petrified Wood and Mineral Resources at Nakhon Ratchasima Rajabhat University, and Masateru Shibata and Yoichi Azuma, again of the Institute of Dinosaur Research at Fukui Prefectural University, and the Fukui Prefectural Dinosaur Museum, describe a new species of Allosauroid Dinosaur from the Early Cretaceous Khok Kruat Formation of Nakhon Ratchashima Province in northeastern Thailand.

The Khok Kruat Formation forms the uppermost unit of the Khorat Group and is widely distributed in the Khorat Basin of northeastern Thailand. The formation is 430–700m thick and consists mainly of reddish-brown siltstones and sandstones, laid down in a fluvial (river) environment. The formation is of Aptian age, between 125 and 113 million years old. The Khok Kruat Formation has produced a number of Dinosaur fossils, most of them from the Ban Saphan Hin (Saphan Hin Village) site in the northwest of the Muang District in Nakhon Ratchashima Province, which has been excavated by the Japan-Thailand Dinosaur Project.

Locality map of new Theropod material and stratigraphy of Khorat Group. (A) map of Nakhon Ratchasima Province, Thailand; (B) distribution map of the Khok Kruat Formation in Nakhon Ratchasima Province; (C) enlarged locality map of Suranaree and Khok Kruat subdistricts with the subdistrict boundaries; (D) a photograph of the excavation site; (E) stratigraphic column of the Khorat Group. A red-coloured star indicates the new Theropod locality, the dotted lines indicate the subdistrict boundaries, and the grey-colored lines indicate the roads in (C) respectively. Chokchaloemwong et al. (2019).

The new species is named Siamraptor suwati, where 'Siamraptor' means 'Thailand thief' and 'suwati' honours Suwat Liptapanlop, who supports and promotes the work of the Northeastern Research Institute of Petrified Wood and Mineral Resources. The new species is described from disarticulated cranial and postcranial elements from at least three individuals. This material comprises three right premaxillae, a right and a left maxillae, a left jugal, two posterior parts of the left mandible comprising the surangular, prearticular, and articular, a posterior part of the left mandible comprising the surangular and prearticular, three anterior cervical vertebrae, three posterior dorsal vertebrae, a middle caudal vertebra, a manual ungual, a right ischium, a distal part of the right tibia, and a left pedal phalanx IV-1. All of these are materials were found in a small area (125 m x 160 m) of a single layer of a single locality, and the overlapping materials exhibit the same diagnostic features.

Skeletal reconstruction of Siamraptor suwati. Cranial elements were scaled to fit in with the holotype (surangular). Scale bar equals 1 m. Chokchaloemwong et al. (2019).

Siamraptor suwati is adjudged to be an Allosauroid on the basis of a straight ventral margin on the jugal (cheekbone), a dorsoventrally deep anterior process below the orbit, a surangular (bone at the back of the jaw) with a deep oval concavity at the posterior end of the lateral shelf and four posterior
surangular foramina (openings), a long and narrow groove along the suture between the surangular and prearticular bones, an articular bone with a foramen at the notch of the suture with prearticular bone, an anterior cervical vertebra (formost vertebra in the neck) with an additional pneumatic foramen in the  parapophysis (transverse processe that projects from the centrum of the vertebra), and cervical and posterior dorsal vertebrae penetrated by a pair of small foramina bilaterally at the base of neural spine. 

See also...

 

Follow Sciency Thoughts on Facebook.

Moros intrepidus: A small Tyrannosauroid Theropod from the early Late Cretaceous of Utah.

Tyrannosauroids were the top predators in latest Cretaceous ecosystems in Asia and North America, reaching sizes of up to nine metres and having adaptive features such as rapid growth, specialised bone-crushing jaws and apparently well-developed senses of smell and vision. However, their time as top predators appears to have been limited to the last 15 million years of the Cretaceous, with the group having a much longer history as smaller predators, first appearing in the Middle Jurassic but being overshadowed by larger groups such as the Allosaurs. How the Tyrannosauroids made this transition from small to large predators is difficult to understand, particularly as the transition appears to have happened in North America, where there is a long gap in the Tyrannosauroid fossil record, between the small species of the Jurassic and Early Cretaceous, and the large species that appeared at the End Cretaceous. 

In a paper published in the journal Communications Biology on 21 February 2019, Lindsay Zanno of Paleontology at the North Carolina Museum of Natural Sciences, the Department of Biological Sciences at North Carolina State University, and the Section of Earth Sciences at the Field Museum of Natural History, Ryan Tucker of the Department of Earth Sciences at Stellenbosch University, Aurore Canoville, Haviv Avrahami, and Terry Gates, also of Paleontology at the North Carolina Museum of Natural Sciences and the Department of Biological Sciences at North Carolina State University, and Peter Makovicky, also of the Section of Earth Sciences at the Field Museum of Natural History, describe a new species of small Tyrannosauroid from the earliest Late Cretaceous Cedar Mountains Formation of Utah. 

The new species is named Moros intrepidus, where ‘Moros’ means ‘impending doom’ and ‘intrepidus’ means ‘intrepid’. The species is described from a partial right hindlimb, comprising portions of the femur, tibia, fourth, and second metatarsals and phalanges of the fourth digit, excavated from the ‘Stormy Theropod’ exposure of the Cedar Mountains Formation in Emery County, Utah, the precise location of which is restricted by Utah state statute. Analysis of zircons from the same horizon suggests that the specimen is no more than 96.4 million years old. 

Right femur of Moros intrepidus. (a) Lateral, (b) cranial, (c) medial, (d) caudal, (e) proximal, and (f) distal views. Partial mid-diaphyseal cross-section of the femur shown in (g) polarized light with lambda filter, (h) natural light with numbered arrows and tracings indicating seven growth cycles, and (i) polarized light. Abbreviations: ar adductor ridge, at accessory trochanter, Ca caudal aspect, Cr cranial aspect, ft fourth trochanter, if intercondylar fossa, inf intertrochanteric nutrient foramen, L lateral aspect, L2 lobe on lesser trochanter, lic linea intermuscularis caudalis. lt lesser trochanter, M medial aspect, mdc mesiodistal crest, pf popliteal fossa, pld lateral depression, proximal. pnf principle nutrient foramen, sat semicircular accessory tuberosity, ts trochanteric shelf. Scale bars (a)–(e) 5 cm; (g)–(i) 1mm. Zanno et al. (2019). 

As well as the hindlimb, Zanno et al. describe two isolated premaxillary teeth from separate exposures of the Cedar Mountains Formation at Suicide Hill and the Cliffs of Insanity. These are flattened in aspect with one concave edge, interpreted as the inner surface, and distinct carinae (grooves) on their front and back surfaces, all features typical of Tyrannosauroids. 

 (c) Silhouette of Moros intrepidus showing recovered elements. Isolated indet. tyrannosauroid premaxillary tooth recovered from nearby strata in (d) occlusal, (e) mesiodistal, and (f) lingual views. Holotype specimen of Moros intrepidus composed of (g) femur, (h) tibia, (i) fourth metatarsal, (j) second metatarsal, and (k) pedal phalanges of the fourth digit. Scale bar (c) 1 m, (g)–(k) 5 mm. (d)–(f) Enlarged to show detail, not to scale. Zanno et al. (2019). 

Based upon the size of the known bones, Moros intrepidus is estimated to have had a mass of about 78 kg. Examination of the microstructure of the bones of the specimen suggests that it was at least six-to-seven years old when it died (Tyrannosauroids are known to have had seasonal growth, resulting in bands of denser material within their bones that form growth rings similar to those seen in trees; because bone is sometimes re-absorbed by the body during growth, this cannot provide as an absolute age, but counting the rings does give a rough minimum age for a specimen). This implies a growth rate similar to that seen in Jurassic Asian Tyrannosauroids such as Guanlong wucaii, a specimen of which with a similar size to Moros intrepidus has been estimated to have been about seven years old when it died, and is in marked contrast to later North American Tyrannosaurids such as Gorgosaurus ibratus, which would have been around three times as large at a similar age. This suggests that the emergence of large Tyrannosauroids really was restricted to the last few million years of the Cretaceous, and may have been closely linked to the disappearance of the earlier large Allosaurs.

Phylogenetic relationships, chronostratigraphic, and palaeoecological implications of Moros intrepidus. (a) Graphic illustrating temporal range of North American Tyrannosauroids including species-level range prior to the discovery of Moros intrepidus, extension of current range, and hypothesized range based on isolated teeth. The current gap in the North American Tyrannosauroid record spans from the Tithonian to the Aptian. Faunal composition of Late Cretaceous ecosystems was established between the Albian and Turonian, as recognized by the stratigraphic appearance of major clades. (b) generalized phylogenetic relationships of Tyrannosauroidea, showing the appearance of select traits related to cursoriality in Tyrannosaurs that are newly optimized as a result of the discovery of Moros intrepidus. (c) Stratigraphic distribution of Allosauria in North America (including Megaraptora) documents overlap with Moros intrepidus in early Late Cretaceous ecosystems leading to (d) refined calibration on the origin of late diverging Tyrannosauroids and clade-level faunal turnover within apex predator roles throughout the Late Jurassic–Late Cretaceous of North America. Coloured polygons are stylized call-outs and are not intended to reflect two dimensional data. Zanno et al. (2019). 

See also...

Follow Sciency Thoughts on Facebook.

Evidence of giant Theropods from the Late Jurassic of Asturias, Spain.

During the Late Jurassic high sea levels reduced Europe to a series of island land masses, with variable faunal affinities to both East Asia and North America. The Iberian Massif comprising Portugal and western Spain is one of the few European landmasses of the time to preserve terrestrial faunas in situ (most fossils of Late Jurassic land animals from Europe are known form shallow marine deposits) including numerous Dinosaur trackways. The Vega, Tereñes and Lastres formations of the Asturias Region of northern Spain has produced numerous Dinosaur trackways, as well as the remains of Stegosaurs, Ornithopods, Sauropods and Theropods, though these are fragmentary and consist largely of isolated bones and teeth. Theropods are known from very little material, including a few isolated teeth and a caudal (tail) vertebra, which has not previously been discovered in any detail.

In a paper published in the journal PeerJ on 5 July 2018, Oliver Rauhut of the Bayerische Staatssammlung für Paläontologie und Geologie, and the GeoBioCenter, and Department for Earth and Environmental Sciences at Ludwig-Maximilians-University, Laura Piñuela of the Museo del Jurásico de Asturias, Diego Castanera, also of the Bayerische Staatssammlung für Paläontologie und Geologie, and the GeoBioCenter at Ludwig-Maximilians-University, and José-Carlos García-Ramos and Irene Sánchez Cela, also of the Museo del Jurásico de Asturias, formally describe the Asturian 

The vertebra is referred to by the specimen number MUJA-1913; it is an anterior caudal vertebra (tail vertebra from close to the body) from a calcareous conglomerate within the Vega Formation. Most of the centrum is preserved, as is the base of the neural arch (dorsal section of the vertebra, including the channel through which the spinal cord runs), but none of the processes upon the neural arch. The forward surface of the centrum has been heavily eroded, but the posterior surface is well preserved, being concave and 140-145 mm in diameter. The centrum is about 150 mm high and 90 mm deep, with an anterior (forward) surface offset from the posterior surface. The neural canal is about 35 mm wide.

Anterior caudal vertebra of a giant megalosaurid from the Vega Formation, MUJA-1913. (A) Left lateral view. (B) Posterior view. (C) Ventral view. (D) Dorsal view. Study sites: ch, chevron facet; d, depression on anterior end of dorsal surface of transverse process; l, lamina dividing the conical postzygocentrodiapophyseal fossa from a shallow dorsal depression; pcd, pleurocentral depression; pcdf, postzygocentrodiapophyseal fossa; pcdl, posterior centrodiapophyseal lamina; vg, ventral groove. Scale bar is 50 mm. Oliver Rauhut and Diego Castanaera in Rauhut et al. (2018).

The size of MUJA-1913 is exceptional, at 150 mm in height it is 15%  larger than the anterior caudal vertebrae of Torvosaurus, the largest known Therapod from the Late Jurassic of the Iberian Massif, and the largest recorded Theropod from Europe to date, and 10% larger than the same bone of Spinosaurus aegyptiacus, possibly the largest Theropod Dinosaur ever. The only comparably large caudal vertebrae come from the largest Cretaceous Carcharodontosaurids and Tyranosaurids, and possibly the largest Late Jurassic Allosaurids of North America. The structure of MUJA-1913 is consistent with that of a large Megalosaurid (the group which includes Torvosaurus), probably around 10 m in length.

The tip of a large Theropod Dinosaur was round at the same level within the formation. This is flattened with evenly spaced carinae (ridges on the cutting edge), and an anastomosing (vein-like) ornamentation, consistent with having come from a Megalosaur.

Tip of a large Megalosaurid tooth fromthe Vega Formation. (A) General view in lingual or labial view. (B) Detail of distal serrations and anastomosing enamel ornamentation. Scale bars are 10 mm. Oliver Rauhut and Diego Castanaera in Rauhut et al. (2018).

Rahaut et al. also report a series of new footprints and trackways from the Lastres Formation (which overlies and is slightly younger than the Vega Formation), all of which belong to Therapod Dinosaurs and are greater than 53 cm in length, with the largest being 82 cm in length and 66 mm in width. These fall into two broad groups anatomically, and are suggested to be evidence of the presence both large Megalosaurids and Allosaurids.

Giant Asturian Jurassic footprints, strongly mesaxonic (Morphotype B). (A) MUJA-1263. (B) MUJA-0213, scale bar: 1 m. (C) Specimen still on Argu¨ero sea cliffs. (D–F) Same specimens, photographs with outline drawings to better illustrate track morphology.  José-Carlos García-Ramos in Rauhut et al. (2018).

See also...

Follow Sciency Thoughts on Facebook.

Neovenator salerii: The neuroanatomy of the rostrum of an Early Cretaceous Allosauroid Dinosaur.

Neovenator salerii is an Early Cretaceous Allosauroid Theropod Dinosaur, known from a single partial skeleton from the Wessex Formation of the Isle of Wight. The skull of this skeleton is exceptionally well preserved, being deep and laterally (sideways) flattened, with blade-like teeth. This has been interpreted as indicative of a terrestrial apex predator, with a hunting technique that is likely to have involved targeting soft tissues, then defleshing with the sharp teeth, but avoiding biting down on bone or other hard tissue, which would produce wear marks on the teeth that are not seen (this is seen in some modern predators, such as Cheetahs).

In a paper published in the journal Scientific Reports on 16 June 2017, Chris Tijani Barker and Darren Naish of the National Oceanography Centre at the University of Southampton, Elis Newham and Orestis Katsamenis of the Faculty of Engineering and the Environment, also at the University of Southampton, and Gareth Dyke of the Department of Evolutionary Zoology and Human Biology at the University of Debrecen, and the Center for Interdisciplinary Biosciences at Pavol Jozef Safarik University, describe the results of a study of the cranial morphology of Neovenator salerii using microfocus μCT to investigate the distribution of its rostral foramina (the openings of channels within the bones of the snout through which nerves and blood vessels pass)and any internal preservation.

Barker et al. found that Neovenator salerii has an extensive network of channels within its maxilla and premaxilla running laterally (to the outside of) the dental alveoli, and connected to opening on the outer side of the bone. This is interpreted as part of the neurovascular system, occupying at least 7.3% and 6.7% of the internal volume of the premaxilla and maxilla, respectively. 

Complex anastomosing neurovasculature surrounding infilled dental alveoli of the premaxilla of Neovenator. (A) Volume rendering of left premaxilla in lateral view with foramina highlighted (blue). (B) Volume rendering of infilled voids. Barker et al. (2017).

Similar structures have previously been found in Pliosaurids (Mesozoic Marine Reptiles) and the Spinosaurids Spinosaurus and Baryonyx (Theropod Dinosaurs interpreted as having been partially aquatic). For this reason, the structures have been interpreted as sensory in nature, used to detect potential prey moving in the water. However, Neovenator appears to have no adaptations to an aquatic lifestyle, suggesting that the channels must have a different purpose.

Similar channels are found in a number of living animals notably some species of Birds, particularly those that engage in probe feeding, such as Kiwis (Apterygidae), Waders (Scolopacidae), and Ibises (Threskiornithidae), as well as in Ducks and Geese (Anseriformes), which use their beaks in a variety of ways for the detection, recognition, and transport of food, and Parrots (Psittaciformes), which are capable of extremely fine manipulation of objects with their beaks, including tool use. Beaks are known in a range of non-Avian Dinosaurs, including many Ornithischians and some Theropod groups, such as Ornithomimosaurs, Therizinosaurs, Oviraptorosaurs and some Ceratosaurs, but there is no evidence of any such structure in any Allosauroid, and nothing known about the biology of Neovenator suggests that it might have had a beak. 

Complex anastomosing neurovasculature surrounding infilled dental alveoli of the maxilla of Neovenator. (A) Volume rendering of left maxilla in lateral view with foramina highlighted (blue). (B) Volume rendering of infilled voids. Abbrevations: aor: antorbital ridge; asr: ascending ramus; ifs: interfenestral strut; laof: lateral antorbital fossa; maf: maxillary alveolar foramina; mcf: maxillary circumfenestra foramina; mfe: maxillary fenestra; mmf: medial maxillary foramina; pab: preantorbital body; pne: pneumatic excavation. Barker et al. (2017).

Channels of this type are also known in modern animals which lack beaks, notably Crocodylians, where it is associated with the detection potential prey moving in the water (as has been speculated for Pliosaurids and Spinosaurids), as well as temperature regulation. The very narrow snout seen in Neovanator makes a role in temperature regulation unlikely, as the snout would have shed excess heat (the only real issue for an animal this size) very efficiently without it. This makes it likely that the channels seen in the maxillary bones of Spinosaurus did indeed carry nerves rather than blood vessels. Barker et al. therefore speculate that the species, and other large Theropods such as Tyranosaurids, was probably capable of highly controlled snout movements, both when subduing prey and manipulating food, and that this would have been useful to an animal which needed to avoid brining very sharp, but not particularly strong, teeth into contact with the bone or other hard tissues of its prey.

See also...

Follow Sciency Thoughts on Facebook.