Hadrosauroid eggs with embryos from the Late Cretaceous of Jiangxi Province, China.

A wide variety of Dinosaur eggs are now known from sites around the world, although eggs with embryos within remain relatively rare. For example, the Hadrosauroids, a large and diverse group of Dinosaurs, have embryonic forms assigned to only three species, Hypacrosaurus stebingeri, Maiasaura peeblesorum, and Saurolophus angustirostris. As a consequence of this, the earliest stages of Dinosaur development are nor well understood, and any new material of great interest to Dinosaur palaeontologists.

In a paper published in the journal BMC Ecology and Evolution on 9 May 2022, Lida Xing of the  State Key Laboratory of Biogeology and Environmental Geology, and School of the Earth Sciences and Resources at the China University of Geosciences, and the Yingliang Stone Natural History Museum,  Kecheng Niu, also of the Yingliang Stone Natural History Museum, Tzu‑Ruei Yang of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, and the Taiwan National Museum of Natural Science, Donghao Wang, also of the School of the Earth Sciences and Resources at the China University of Geosciences, Tetsuto Miyashita of the Beaty Centre for Species Discovery and Palaeobiology Section at the Canadian Museum of Nature, and Jordan Mallon, also of the Beaty Centre for Species Discovery and Palaeobiology Section at the Canadian Museum of Nature, and of the Department of Earth Sciences at Carleton University, describe two Hadrosauroid embryos from the Late Cretaceous Hekou Formation red beds of the Ganzhou Basin in Jiangxi Province, China.

Hadrosaurs have traditionally been divided into two groups, the Hadrosaurines, with solid crests, and the Lambeosaurines, with hollow crests. However, a revision of the taxonomy of the group in 2010 suggested that the species Hadrosaurus foulkii, from which the group takes its name, in fact lies outside the Hadrosaurinae, forming a sister group to the (Hadrosaurinae + Lambeosaurinae). If this is the case, then it is inappropriate for the Hadrosaurinae to be named after a species which falls outside the group, which has led to it being renamed the Saurolophinae. Since 2010 there have been several further attempts at resolving the phylogeny of the Hadrosauridae, some of which have recovered Hadrosaurus foulkii as falling outside the Hadrosaurinae (or Saurolophinae), while others have returned it to this group. In the absence of any clarity on this issue at this time, Xing et al. favour the term Hadrosaurine to describe Hadrosaurs with solid crests, without placing any phylogenetic implications on this usage.

Both embryos described came from a clutch which is recorded as having comprised 13 eggs at the time of discovery (the actual number may have been larger). The eggs themselves are not well preserved, but appear to have originally had a prolate spheroid shape (i.e a slightly lemon-shaped sphere), consistent with eggs of the oofamily Spheroolithidae, which is otherwise known from the Hekou Formation. However Xing et al. do not attempt to assign the eggs to a more specific taxon, as their shells are too poorly preserved to allow examination of their microstructure.

Eggshell of Spheroolithidae sp. (YLSNHM 01373). (A) Overview of egg containing embryonic Hadrosauroid; (B) cross‑section of the YLSNHM 01373 eggshell under transmitted, unpolarized light. The dotted line marks the boundary between the mammillary (ML) and continuous (CL) layers. The white arrows indicate the locations of organic cores. Xing et al. (2022).

The first egg examined, (YLSNHM 01328) contains a partial articulated skeleton comprising the posterior part of the cranium, the complete series of cervical vertebrae, plus the forward part of the dorsal vertebral column and the associated ribs. Unfortunately the missing part of the skull includes the site where the palatal process of the maxilla, if present, would be found. This is unfortunate, as this is a reliable taxonomic trait within the Hadrosauridae, being present in the Hadrosaurinae and absent in the Lambeosaurinae. 

Hadrosauroid partial embryonic skeleton (YLSNHM 01328). (A) Photograph, (B) interpretive drawing. Xing et al. (2022).

The squamosal of YLSNHM 01328 is most similar to that of Tanius sinensis,  Levnesovia transoxiana,  and Nanningosaurus dashiensis (Nanningosaurus dashiensis is considered a Lambeosaurine, while the other two are known only from partial remains and cannot be assigned with confidence to the Hadrosaurinae or Lambeosaurinae), although the postorbital process of this bone is longer than in most Hadrosaurs of any type.

Hadrosauriform squamosals in left lateral view. Xing et al. (2022).

The second specimen, YLSNHM 01373 comprises a partial skeleton lacking parts of the skull, the tail, and the ends of the limbs. This specimen has a well preserved parietal bone, which can be seen to be elongate, as in Hadrosaurine, but not Lambeosaurine, Hadrosaurs. The specimen also has a well preserved tooth row, which has become detached from the its original position, although it is unclear whether that was on the upper or lower jaw. Assuming the first rib is attached to the first dorsal vertebra, YLSNHM 01373 has eleven cervical vertebrae, but it is unclear whether the first two visible cervical vertebrae are the atlas and axis (first two vertebrae) or whether these are hidden, so this number might be higher. 

Hadrosauroid partial embryonic skeleton (YLSNHM 01373). (A) Photograph, (B) interpretive drawing. Xing et al. (2022).

Both sets of embryonic remains can be confidently assigned to the Hadrosauridae, but lack sufficient diagnostic features to assign them to either the Hadrosaurinae or the Lambeosaurinae. One feature not dependent on morphology which has been suggested for differentiating these groups is size; it has been observed that, in Montana at least, Hadrosaurine eggs and embryos tend to be smaller than those of Lambeosaurs. Based upon femur lengths, the Hekou Formation embryos are closer to the Montana Hadrosaurines than the Montana Lambeosaurines (in fact they are slightly smaller). However, the Hekou Formation embryos do not fill their eggs, making it highly likely that they were some way short of hatching when they died, so this cannot realistically be used as a diagnostic feature in this case.

Reconstruction of a Hadrosauroid embryo, based on YLSNHM 01373. Ren W.‑Y.  in Xing et al. (2022).

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Analysing the skin of an exceptionally well-preserved Hadrosaur from the Late Cretaceous Wapiti Formation of Alberta, Canada.

Fossilised Dinosaur integument has been known for nearly 150 years, yet it is only recently that it has been considered more than a simple impression (trace fossil) of the original skin surface. Although feathers and filamentary protofeathers of Avian and non-Avian Theropods have received considerable attention, particularly in the past two decades, squamous (scaly) skin is more widespread and was probably plesiomorphic (the original state) in Dinosaurs. Significant advances in our understanding of the preservation and structure of squamous skin have been achieved with the use of synchrotron radiation techniques, and it is now generally accepted that labile tissues, such as skin and muscle, can preserve and remain intact millions of years after the death of the organism. Hadrosaur skin is relatively common in the fossil record, but few studies have investigated either its composition or the possible determining factors behind its preservation.

In a paper published in the journal PeerJ on 16 October 2019, Mauricio Barbi of the Department of Physics at the University of Regina, Phil Bell of the School of Environmental and Rural Science at the University of New England, Federico Fanti of the Dipartimento di Scienze Biologiche, Geologiche e Ambientali and the Museo Geologico Giovanni Capellini at the Università di Bologna, James Dynes of Canadian Light Source Inc. at the University of Saskatchewan, Anezka Kolaceke, also of the Department of Physics at the University of Regina, Josef Buttigieg of the Department of Biology at the University of Regina, Ian Coulson of the Department of Geology at the University of Regina, and Philip Currie of Biological Sciences at the University of Alberta, describe the results of a study of a study of a sample of three-dimensionally preserved squamous skin from a Hadrosaurid dinosaur from the Late Cretaceous Wapiti Formation, discovered near the city of Grande Prairie in Alberta, Canada.

The Wapati Formation of the Western Canadian Sedimentary Basin outcrops across parts of northwestern Alberta and northeastern British Colombia. It is a series of sandstones, siltstones, mudstones and related deposits laid down in a broad floodplain associated with a meandering river system between the Campanian (83.6-72.1 million years ago) and the Palaeocene (66-56 million years ago). The Cretaceous portion of this formation has yielded a variety of Dinosaur fossils, though most of the fossil-producing exposures are in inaccessible locations, limiting palaeontological efforts.

The speciemen examined by Barbi et al., UALVP 53290, is an incomplete Hadrosaur recovered from the Red Willow Falls locality, less than one kilometre to the east of the Alberta-British Columbia border. In this area, late Campanian deposits of the Wapiti Formation have been dated at 72.58 million years old and consist of repeating fining-upward sequences of crevasse-splays, muddy and organic-rich overbank deposits, and minor sandy channel fills. Sandstones are primarily formed by poorly-sorted quartz, feldspar, and carbonate clasts, commonly presenting a carbonatic cement. Thin and discontinuous altered volcanic ash beds are found at the top of fining-upward successions, where they are locally interbedded with coal lenses. The specimen comprises an incomplete articulated-to-associated Hadrosaurid skeleton with most of the thoracic region, forelimb and pelvic elements. Parts of the tail likely continue into the cliff but could not be recovered owing to the precipitous nature of the outcrop. The only cranial element found, an incomplete jugal (cheekbone), indicates Hadrosaurine affinities, though the material is not sufficient to diagnose the specimen to species level. Another Hadrosaur specimen recovered from nearby could be assigned to Edmontosaurus regalis, and Barbi et al. consider it likely that UALVP 53290 belongs to the same species.

Sheets of in situ and partially displaced fossilised integument were found close to the forelimbs of UALVP 53290, and occur in two types: as a 2 mm thick black rind preserving the three-dimensionality of the epidermal scales, and as low-relief structures covered in a thin, oxide-rich patina. The skin samples examined by Barbi et al. were slightly displaced relative to their true life position but are presumed to have come from the dorsal (anterior) surface of the forearm. The integument is composed of large (10 mm), hexagonal basement scales identical to scales on the upper surface of the forearm in other Edmontosaurus specimens.

UALVP 53290. (A) quarry map showing location of preserved integument (indicated by numerals) shown in (B) and (C). Dark grey regions are freshwater bivalves. (B) Higher magnification of (1) showing dark-coloured polygonal scales . (C) Detail of (2) showing cluster areas associated with the forearm integument. (D) Detail of dark  scales in oblique view showing sampling locations for spectromicroscopy: samples were collected with a microtome from (i) the outer surface of the epidermal scale to produce a light-coloured powder, and (ii) from a cross section of the scale that penetrated into the pale underlying sedimentary matrix to produce a dark-coloured powder. Scale bar in (A) is 10 cm. Scale bars in (B) (D) are 1 cm. Abbreviations: Dv, dorsal vertebra; H, humerus; Mc, metacarpal; Os, ossified tendon; Pu, pubis; R, rib; Ra, radius; Sc, scapula; Th, Theropod tibia; Ul, ulna. Line drawing by Phil Bell. Barbi et al. (2019).

Scanning Electron Microscope studies of a 20 μm thick cross section of the Hadrosaur skin were conducted with the intention of investigating possible markers that could discriminate the skin from the sedimentary matrix, and (b) identify potential regions for the presence of organic contents.. The thin section covers the first 2 cm of the sample starting from the outer surface of the scales To better understand the morphology of the Hadrosaur skin, histological skin samples were prepared for a Chicken, Gallus gallus domesticus, a Saltwater Crocodile, Crocodylus porosus, and a Rat, Rattus norvenicus, and compared with the Hadrosaur skin.

Optical microscopy of histological samples of the skin from three extant representatives (Gallus, Crocodylus, Rattus) reveals a thin but characteristically multi-layered epidermis and a deeper, thicker dermis. The outermost epidermal layer corresponds to the stratum corneum, a keratinous layer that aids in protection of the internal organs (including the underlying epidermal and dermal layers) from desiccation. The stratum corneum, which is composed of stratified layers of β -keratin, is the thickest component of the epidermis in Crocodylus owing to the presence of keratinised scales. As a result of this cornified layer, the epidermis is also the thickest in Crocodylus in both absolute and relative terms. The stratum corneum is comparatively thin in both Rattus and Gallus, but where epidermal scales are present on the avian podotheca, such as Gallus, they are similarly covered by a thick stratum corneum, although these were not sampled in this study. In Birds, the relative thickness of the epidermal layers differs between locations, however, the epidermis is consistently thinner in Gallus than it is in Rattus and Crocodylus, a feature that has been linked to the progressive lightening of the Avian body and the evolution of flight.

In Crocodylus, the epidermis is invaginated to form the hinge area between scales. Much deeper invaginations, invading both the epidermis and dermis, are formed by hair and feather follicles in Rattus and Gallus, respectively. Underlying the epidermis is the dermis, which contains openings for the blood vessels, fat deposits, and abundant pigment cells, the latter of which are more diverse in Crocodylus and other reptiles due to their naked skin. Glands are relatively scarce and/or small in Avian and Reptilian skin, but are a salient feature of Mammalian dermis. Thick subcutaneous hypodermis dominated by fat stores and blood vessels underlies the dermis in both Gallus and Rattus, whereas it is relatively thin in Reptiles and was not sampled in the specimen of Crocodylus.

Phase-contrast optical microscopy of the Hadrosaur skin reveals an outermost (superficial) dark-coloured layer 35 75 μm in thickness, which overlies the sedimentary matrix This outer layer is composed of clearly-defined, alternating dark and lighter-coloured layers, which typically range from ~5 mm to ~15 μm in thickness. Individual layers are typically laminar or undulatory giving the entire outer layer a stratified appearance. These finer layers may deviate around sedimentary particles that are occasionally found embedded within the outer dark layer. Aside from these occasional particles, sedimentary grains are typically restricted to the sedimentary matrix underlying the dark outer layer. In places, the dark layers appear to be composed of oval substructures measuring a few micrometers in maximum dimension. The entire dark stratified layer is, in places, capped by a pale-coloured, faintly laminated region identified as barite. No other evidence of integumentary features that could be interpreted as hair follicles, feathers or glandular structures could be identified anywhere in the sample. Other epidermal/dermal features such as osteoderms and melanosomes are also absent.

Comparative histology (transmitted light optical micrographs) of the skin of Edmontosaurus cf. regalis (UALVP 53290) (A), (B) Crocodylus porosus (C), (D), Rattus rattus (E), (F) and Gallus gallus domesticus (G), (H). In UALVP 53290, the dark outer (superficial) layer corresponds to the position of the epidermis (e) in modern analogues (C)-( F). The thickness of the region identified as epidermis in UALVP 53290 varies (B); however, distinctive layering of this region (arrowheads in B) resembles the stratified appearance and general thickness of the stratum corneum in Crocodylus (D). Boxed area in (A) encompasses the enlarged area shown in (B). (I) Phase-contrast and (J) transmitted light optical micrographs of Edmontosaurus cf. regalis (UALVP 53290) skin revealing fine laminae in the outer stratified region. The outermost epidermal layer in indicated by arrowheads. Dark laminae are, in places, composed of small, lenticular or subcircular bodies (arrows in (I)). Abbreviations: b, barite layer; e, epidermis; d, dermis; ds, dark stratified region; g, sedimentary grains; h, hinge area; hs, hair shaft; hy, hypodermis; m, sedimentary matrix; p, pigment cells; s, epidermal scale; sc, stratum corneum; sg, stratum germinativum. Barbi et al. (2019).

Histological sampling of the Hadrosaur skin reveals microscopic details of the dark outer layer associated with a single epidermal scale. Specifically, this layer is distinctly stratified, composed of alternating dark and lighter-coloured layers with a total thickness of 75 μm. The topological position, overall thickness and stratified composition of the dark outer layer in UALVP 53290 is strongly reminiscent of the stratum corneum in Crocodylus ( ~145 μm thick in Crocodylus), which forms the thickest component of the epidermis in the latter. In contrast, the entire epidermis is extremely thin in both Rattus and Gallus (less than 25 μm) and the thickness of the stratum corneum is negligible compared to Crocodylus. Given the obviously scaly epidermal covering of Hadrosaurs, including UALVP 53290, it seems reasonable to infer that the dark-coloured stratified layer represents the mineralised remains of the stratum corneum. The differing thickness in what we have identified as the stratum corneum of the Hadrosaur and that of Crocodylus could be attributable to dehydration, diagenesis, taxonomic differences or any combination of these. Similar keratinous structures to those identified in UALVP 53290, together with intact remains of α - and β-keratins have been reported in non-avian Dinosaurs and contemporaneous Birds; however, these results are largely restricted to feathers and the cornified sheaths covering the unguals rather than skin.

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Kamuysaurus japonicus: A new species of Hadrosaur from the Late Cretaceous of Hokkaido, Japan.

Hadrosaurs, or Duck-Billed Dinosaurs, were large herbivorous Ornithischian Dinosaurs widespread across Laurasia (Eurasia plus North America; Laurasia split away from the southern continents in the Triassic, the split into North America and Eurasia during the Cretaceous) as well as South America and Antarctica during the Late Cretaceous. They were descended from the earlier Iguanadontids, but with more sophisticated jaws and teeth, which allowed them to chew their food, not by side-to-side motion as in a modern mammal, but by a unique flexion of the upper jaw parts, which moved apart as the lower jaw moved upwards (from which scientists conclude these Dinosaurs must have had lips, unlike any modern relative of the Dinosaurs). The term 'Hadrosauroid' refers to the widest possible grouping of Hadrosaurs, including all animals in the group after their evolutionary split with the Iguanadontids in the Early Cretaceous, whereas the most derived members of the group are split into two subgroups, the Lambeosaurs, which had hollow bony crests, thought to have been used for making sounds, and the Saurolophides, or Hadrosaurines, which either lacked crests or had solid ones.

In a paper published in the journal Scientific Reports on 5 September 2019, Yoshitsugu Kobayashi of the Hokkaido University Museum, Tomohiro Nishimura of the Hobetsu Museum, Ryuji Takasaki of the Department of Natural History and Planetary Sciences at Hokkaido University, Kentaro Chiba of the Faculty of Biosphere-Geosphere Science at the Okayama University of Science, Anthony Fiorillo of the Perot Museum of Nature and Science, Kohei Tanaka of the Graduate School of Life and Environmental Sciences at rhe University of Tsukuba, Tsogtbaatar Chinzorig of the Division of Vertebrate Paleontology at the Institute of Paleontology and Geology of the Mongolian Academy of Sciences, Tamaki Sato of the Department of Astronomy and Earth Sciences at Tokyo Gakugei University, and Kazuhiko Sakurai, also of the Hobetsu Museum, describe a new species of Hadrosaur from the Late Cretaceous Hakobuchi Formation of Hokkaido, Japan.

The Hakobuchi Formation is the uppermost unit of the Yezo Group, which is a part of a Cretaceous to Paleocene forearc basin deposit that outcrops in southern Hokkaido, Japan. The formation consists of alternating layers of fine- to medium-grained sandstone with hummocky cross-stratification, a bedding pattern typically associated with the action of large storms (such as typhoons) below the fair weather wave base, and sandy mudstones lacking cross-stratification and containing glauconite, a mineral considered indicative of outer shelf environments with low sedimentation rates. The unit of the formation which produced the specimen from which the new species is described has been correlated to the lowest Maastrichtian in age, making it about 72 million years old.

The new Hadrosaur species is named Kamuysaurus japonicus, where 'Kamuysaurus' derives from 'Kamuy', a spiritual or divine being in the mythology of the indigenous Ainu people of Hokkaido, plus '-saurus', the Latin term for a Lizard or Reptile, frequently used as a suffix for Dinosaur names, and 'japonicus' indicates that it comes from Japan. The species is described from a single specimen comprising a nearly complete skeleton with the skull and mandible, derived from an outcrop of the Hakobuchi Formation which is considered to represent an outer shelf environment because of the presence of glauconite sandstone and the absence of hummocky cross-stratification. Despite its completeness, some bones are heavily damaged or eroded by a bio-erosion prior to burial.

(a) The holotype skeleton of Kamuysaurus japonicus. (b) Reconstructed skeleton, showing recovered elements. Selected postcranial elements: cervical vertebrae (atlas, axis, and fourth and twelfth cervicals) in left lateral view (c), dorsal vertebrae (first, seventh, and sixteenth dorsals) in left lateral view (d), caudal vertebrae (anterior, middle, and posterior caudals) in left lateral view (e), left scapula (f) and coracoid (g) in lateral view, right sternum in ventral view (h), left humerus in anterior view (i), right ulna and radius in medial view (j), right manus in dorsal view (k), right pelvis in lateral view (l), right femur in anterior view (m), right tibia in anterior view (n), right fibula in lateral view (o), right astragalus and calcaneum, articulated positioned with tibia (p), and right pes in dorsal view (q). All scales are 10 cm except 1 m scale for (b). Abbreviations; ac, acromion process; ast, astragalus; cal, calcaneum; dpc, deltopectoral crest; fi, fibula; icg, intercondylar groove; il, ilium; is, ischium; ltr, lesser trochanter; mc2, metacarpal II; mc5, metacarpal V; mt2, metatarsal II; mt4, metatarsal IV; nc, neurocentrum; od, odontoid; olp, olecranon process; pc, pleurocentrum; pu, pubis; ra, radius; ti, tibia; ul, ulna; vp, ventral process. Kobayashi et al. (2019).

The specimen is assigned as a Hadrosaurine Hadrosaurid with the following unique characters: the midpoint of the quadratojugal notch is positioned at roughly three-quarters of the total length of the quadrate (a bone in the jaw which forms part of the inner ear in Mammals) from the dorsal end, the ascending process of the surangular (bone in the jaw which has been lost in Mammals) is short, and the neural spines of sixth to thirteenth dorsal vertebrae are inclibed forwards. Kamuysaurus japonicus also has a slightly curved primary ridge on the maxillary(upper) teeth, the high average height/width ratio of the dentary (lower) teeth is over 3.30, there is a moderate medial extension of the symphyseal process of the dentary (jawbone), the anterior margin of the coronoid process of the dentary is more developed than the posterior margin, the triangular ventral margin of the anterior process of the jugal as wide as it is high, the palatine articular facet of the jugal (cheekbone) is moderately inclined, the caudal margin of the quadratojugal flange of the jugal is nearly straight, theanterodorsal margin of the prefrontal (bone that forms the upper inside portion of the orbit) along the orbital rim is smoothly curved, sthe quamosal process of the postorbital (bone that forms the upper outside portion of the orbit) terminates anterior to the quadrate cotylus, the nasofrontal sutural surface of the frontal (connection between the frontal bone, which makes up the forhead, and the bones of the snout) is long, the infratemporal fenestra (opening in the skull behind the eye) is subrectangular, there is a weak expansion of deltopectoral crest of the humerus (long bone in the upper arm), the humerus is slender with the humeral shaft being less than 20% as wide as it is long.

Life reconstruction of Kamuysaurus japonicus with a carcass of a Mosasaur, Phosphorosaurus ponpetelegans, a Sea Turtle, Mesodermochelys undulates, and shells of Ammonoids, Patagiosites compressus and Gaudryceras hobetsense, and Bivalves, Nannonavis elongatus on the beach. The individual of Kamuysaurus in the foreground is reconstructed based on the assumption of the presence of a supracranial crest, similar to a sub-adult form of Brachylophosaurus. The individual behind it is reconstructed without the crest. Kobayash et al. (2019).

In order to access the somatic maturity of this individual, the right tibia was thin-sectioned. Tibiae have been often used for osteohistological examination of Hadrosaurs, because they have a thick cortex and therefore preserve a more complete record of the growth. This ontogenetic assessment indicated that this individual had reached its somatic maturity. Reconstruction of the specimen as a quadruped gave an estimated body mass of 5296 kg, while reconstruction as a biped gave a mass of 4087 kg; in both reconstructions the body length is about 8 m and no further significant growth could have been expected if the animal had continued living.

Carcass of Kamuysaurus, floating in the sea, with two Mosasaurs, Mosasaurus hobetsuensis, two Sea Turtles, Mesodermochelys undulates, and four Ammonoids, Pachydiscus japonicus. Kobayashi et al. (2019).

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Datonglong tianzhenensis: A new non-Hadrosaurid Hadrosauroid from the Late Cretaceous of Shanxi Province, China.

The Late Cretaceous Huiquanpu Formation of Tianzhen County in Shanxi Province, China, has been excavated for Dinosaur remains since the 1980s, during which time it has produced over 2300 individual specimens, including Ankylosaurs, Sauropods, Theropods and Hadrosaurids.

In a paper published in the journal Vertebrata PalAsiatica on 1 March 2016, Xu Shi-Chao of the Shanxi Museum of Geology, You Hai-Lu of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Wang Jai-Wei of the Faculty of Geology at the Lomonosov Moscow State University, Wang Suo-Zhu and Yi Jian, also of the Shanxi Museum of Geology, and Jia Lei, again of the Shanxi Museum of Geology and of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology, describe a new species of non-Hadrosaurid Hadrosauroid (Ornithischian Dinosaur more closely related to the Hadrosaurs than to the Iguanadontids, but not considered to be a true Hadrosaurid) from the Huiquanpu Formation.

The new species is named Datonglong tianzhenensis, where 'Datonglong' means 'Dragon of Datong' (the major city in the area where the fossil was found) and 'tianzhenensis' means 'from Tianzhen'. The species is described from a single almost complete right dentary, 34 cm in length, missing its rostral end (back) and the rostral part of the tooth row.

Photos of right dentary of Datonglong tianzhenensis in (A) lateral view, (B) medial view, (C) dorsal view, (D) caudal view; (E) close-up of partial dentition in (B), not in scale. Xu et al. (2016).

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Probrachylophosaurus bergei: A new species of Brachylophosaurin Hadrosaur from the Late Cretaceous of northern Montana. Hadrosaurs were large, herbivorous Ornithischian Dinosaurs, commonly referred to as...

Ugrunaaluk kuukpikensis: A new species of Hadrosaurid Dinosaur from the End Cretaceous of Alaska.                                       The Prince Creek Formation of Northern Alaska is noted for the production of numerous End...

A Hadrosaurid Dinosaur trackway from the Denali National Park in Alaska.                        The preserved tracks of ancient animals such as Dinosaurs can provide insights into their lifestyles and biology that could not be determined by examination of bones alone, although such data needs to be interpreted carefully. Such studies can potentially provide data on herding or other social structures among extinct animals, as well as data on the movement of...

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A Hadrosaurid Dinosaur trackway from the Denali National Park in Alaska.

The preserved tracks of ancient animals such as Dinosaurs can provide insights into their lifestyles and biology that could not be determined by examination of bones alone, although such data needs to be interpreted carefully. Such studies can potentially provide data on herding or other social structures among extinct animals, as well as data on the movement of individual creatures.

In a paper published in the journal Geology on 30 June 2014, Anthony Fiorillo of the Perot Museum of Nature and Science, Stephen Hasiotis of the Department of Geology at the University of Kansas and Yoshitsugu Kobayashi of the Hokkaido University Museum describe a newly discovered Dinosaur trackway in the Denali National Park in Alaska.

The trackway appears to show the movements of a large number of Hadrosaurid Dinosaurs. It is found in the lower part of the Late Cretaceous Cantwell Formation, which comprises fluvial (riverine) deposits preserved in a highly seasonal environment. The site is thought to be close to the same position that it occupied during the Late Cretaceous, i.e. it would have been within the Arctic Circle at the time when the tracks were laid down. Arctic ecosystems during the Cretaceous are thought to have been unlike anything found in the modern world, as the greenhouse climate of the period prevented the formation of permanent ice caps, but within the Arctic Circle the winter would still have been marked by several months of complete darkness.

Polar projection of tectonic plates during the Late Cretaceous, with inset map of Alaska. NA—North America. Dots in both maps indicate location of Denali National Park. Fiorillo et al. (2014).

The tracks appear to have been laid down over a short period of time (based upon analysis of plant and invertebrate fossils in the deposits, which are thought to have been highly seasonal) leading Fiorillo et al. to conclude they represent the passage of a single herd of animals. This herd apparently contained individuals with a wide range of sizes, from mature individuals, to very young juveniles. This is interesting as Hadrosaurid tracks in more southerly locations have previously shown only individuals of a single size, suggesting that the animals moved in packs determined by age. In contrast the Denali Herd appears to have contained animals of different ages, suggesting that younger animals were incorporated into a multi-generation herd, which in turn implies that extended parental care may have been occurring.

(A–C) Size ranges of tracks found at Denali National Park, Alaska, tracksite. (D) Adult Hadrosaurid track with skin impressions. Scale bar for (C1) is 5 cm.Fiorillo et al. (2014).

Fiorillo et al. also observe that while there appear to have been Hadrosaurs of all sizes in the pack, the size distribution is skewed towards larger, presumably adult, specimens. They suggest that this may be indicative of rapid growth in juvenile Hadrosaurs, with a lifecycle that includes a short growing period followed by an extended adult phase (something that has been suggested for Hadrosaurs previously).

Relative frequencies of each growth stage as function of body mass in the Denali Hadrosaur herd. This curve independently corroborates hypothesised growth curve for Hadrosaurid dinosaurs proposed by others. Fiorillo et al. (2014).

It has been suggested that Dinosaurs living within the Arctic Circle may have migrated seasonally to escape the dark winter season, in a similar way to the long distance migrations of modern Caribou. Based upon our understanding of the location of the Dinali site during the Cretaceous, and the sizes of the Dinosaurs within this pack (which affects the distance an animal can migrate by walking), Fiorillo et al. suggest that it would have been impossible for the Dinali herd to migrate seasonally from the site to a location outside the Arctic Circle, suggesting that they were able to overwinter in the Arctic.

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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...

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

Dinosaur footprints are well documented from a number of sites...

Early Cretaceous Dinosaur footprints from Sichuan Province, China.

 

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A new species of Hadrosauroid Dinosaur from the Late Cretaceous of Shanxi Province, China.

Hadrosaurs, or Duck-Billed Dinosaurs, were large herbivorous Ornithischian Dinosaurs widespread across Laurasia (Eurasia plus North America; Laurasia split away from the southern continents in the Triassic, the split into North America and Eurasia during the Cretaceous) during the Late Cretaceous. They were descended from the earlier Iguanadontids, but with more sophisticated jaws and teeth, which allowed them to chew their food, not by side-to-side motion as in a modern mammal, but by a unique flexion of the upper jaw parts, which moved apart as the lower jaw moved upwards (from which scientists conclude these Dinosaurs must have had lips, unlike any modern relative of the Dinosaurs). The term 'Hadrosauroid' refers to the widest possible grouping of Hadrosaurs, including all animals in the group after their evolutionary split with the Iguanadontids in the Early Cretaceous, whereas the most derived members of the group are split into two subgroups, the Lambeosaurs, which had hollow boney crests, thought to have been used for making sounds, and the Saurolophides, which either lacked crests or had solid ones.

In a paper published in the journal PLoS One on 18 October 2013, a team of scientists led by Run-Fu Wang of the Shanxi Museum of Geological and Mineral Science and Technology describe a new species of Hadrosauroid Dinosaur from the Late Cretaceous Zhumapu Formation of Shanxi Province in northern China.

The new species is named Yunganglong datongensis, where 'Yunganglong' refers to the Yungang Grottoes, a group of ancient rock-cut Buddhist temples about 50 km from the site where the specimen was discovered, with the suffix '-long' meaning Dragon, and 'datongensis' refers directly to the site where the specimen was found, in Datong City.

The specimen is described from the caudodorsal part (base) of a skull, two cervical vertebrae, a partial dorsal neural arch and neural processes, two caudal vertebrae, distal portions of both ischia, the distal end of a left femur, proximal portion of a right tibia and the distal portion of a left tibia with astragalus, all presumed to come from the same animal.

The caudodorsal part of the skull of Yunganglong datongensis  (A) Right lateral view. (B) Dorsal view. (C) Caudal view. Scale bar is 10 cm. Wang et al. (2013).

See also A new Lambeosaurine Dinosaur from the French Pyrenees, Dinosaur skeleton vandalized in Alberta, Canada and New species of End Cretaceous Hadrosaur from the Russian Far East.

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