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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Aquilarhinus palimentus: A new species of Hadrosaurid Dinosaur from the Late Cretaceous of Big Bend National Park, south-western Texas.

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. 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 term 'Hadrosaurid' refers to the most derived members of the group, which appeared in the Late Cretaceous and 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 of Systematic Palaeontology on 12 July 2019, Albert Prieto-Marquez of the Institut Catal a de Paleontologia Miquel Crusafont at the Universitat Aut onoma de Barcelona, and the Museu de la Conca Dell a-Parc Cretaci, and Jonathan Wagner and Thomas Lehman of the Departament of Geosciences at Texas Tech University, describe a new species of Hadrosaurid Dinosaur from the Late Cretaceous Aguja Formation of Big Bend National Park, south-western Texas.

The Aguja Formation of western Texas preserves one of the southernmost Campanian ( 83.6  to 72.1 million years old) terrestrial vertebrate faunas in North America. Nearly the entire fauna, however, is known from the uppermost part of the formation (the upper shale member). Until recently, very little was known about the vertebrate fauna found in the lower part of the formation (the lower shale member). S diverse assemblage of small Theropod, Lizard and Mammal teeth (the ‘Lowerverse local fauna’) has been described from a single locality in the lower shale member, as has a more general fauna and stratigraphy, but otherwise the vertebrate fossils of the lower Aguja Formation remain undocumented.

 

Terrestrial and paralic strata of the Aguja Formation are widely exposed in and around Big Bend National Park in south-western Texas. These strata are underlain by and intertongue with marine deposits of the Pen Formation. The Aguja consists of two eastward-thinning intervals of terrestrial strata (the lower and upper shale members) separated by a westward-thinning wedge of interposed marine strata – the McKinney Springs tongue of the Pen Formation. The upper shale member is widely exposed throughout Big Bend National Park and surrounding areas, but the lower shale member is mostly exposed on private ranches west of the park; it thins and pinches out in the south-western part of the park and does not extend into the eastern portion.

 

The lower shale member of the Aguja Formation consists primarily of thick beds of lignitic clay-shale with several prominent sandstone and coal beds, particularly near the base. In the middle of the lower shale member there is a thin zone of interbedded very fine sandstone and carbonaceous mudstone with conspicuous iron-manganese concretions. This concretionary interval is the only part of the lower shale member that yields significant vertebrate fossils, and the holotype specimen of the new Hadrosaurid documented here was collected from these strata. 

 

The lower shale member is interpreted as having accumulated primarily in a coastal swamp or marsh environment. The specimen was recovered from within a bed of mudstone having irregular bedding planes covered with abundant large carbonised leaf and wood fragments, many of which are riddled with Teredolites borings. The bones are partially enclosed in large concretions of iron-manganese oxides. Some of the bones were broken prior to burial, but articulation surfaces are intact and the cortical surfaces exhibit little cracking, indicating that the bones had been subject to minimal transport or weathering prior to burial. Immediately overlying the bone-bearing bed is a thin layer with abundant small Ostreid Bivalve shells, but no other remains are preserved at the site.

 

The vertebrate fauna from the lower shale member dates back to between 81 and 80 million years ago, corresponding to the early Campanian. This fauna may be slightly older than that of the Wahweap Formation in Utah and lower Two Medicine Formation in Montana. Only a few Hadrosaurids have been described from these strata, such as Gryposaurus latidens and Acristavus gagslarsoni (both from the Two Medicine Formation of Montana) and these are among the oldest known Hadrosaurids. The new species from the lower shale member is therefore significant in adding to our understanding of the early evolution and diversity of the group. In particular, this animal is uniquely positioned, both phylogenetically and temporally, to expand our understanding of the early evolution of Hadrosaurid supracranial ornamentation.

The new species is named Aquilarhinus palimentus, where 'Aquilarhinus' means 'Eagle-nosed' and 'palimentus' means 'shovel-chin'. The specimen from which the species is described, TMM 42452-1, comprises a sphenoid fragment, both nasals, the right maxilla, the right jugal, the right quadratojugal, the partial left and right palatines, a partial right dentary, a partial first ceratobranchial, a partial neural arch of atlas, fragments of two cervical centra, two cervical ribs, a partial sacral rib, a left carpal, a nearly complete left manus, the postacetabular process of the right ilium, a fragment of right ischium, a partial astragali, pedal phalanxes III-1, and four pedal unguals. Most of the material was collected in 1983 by Thomas Lehman, Neal LaFon, and Kyle Davies, with the remainder being excavated in 1999 by Jonathan Wagoner and Thomas Lehman. The preserved parts of the skull and jaws were disarticulated but closely associated. All of these bones were found within 4 m² and clearly represent a single individual. This specimen was briefly described by Wagner in 2001 as Kritosaurus sp.  Subsequent study of the specimen, however, indicates that the new species cannot be included within Kritosaurus and differs sufficiently from other Hadrosaurids to warrant recognition a new genus and species.

 

 Geographical and straigraphical location of the type and referred material of Aquilarhinus palimentus. Abbreviations: cg, conglomerate; cl, clay; si, silt; ss, sandstone. Prieto-M arquez et al. (2019).

 

Aquilarhinus palimentus is a Hadrosaurid Dinosaur possessing nasals transversely broad across the skull table; a premaxillary shelf of maxilla at anterior apex flat and as broad as the proximal segment of the palatal process; a palatine extending nearly horizontally to contact the maxilla; and a dorsally reflected symphysial process of the dentary. It differs from all other Hadrosaurids in possessing maxilla combining jugal process and ectopterygoid ridge continuous with ventral margin of jugal facet, and differs from all other Hadrosaurids except Latirhinus uitstlani in having a nasal enclosing the extremely broad and sub-circular lateral profile of the external bony naris.

In general aspect, the skull as reconstructed was almost certainly tall and would have had a steeply sloping facial profile, as in Gryposaurus. There is circumstantial evidence to indicate that the skull roof sloped anteroventrally, and the external bony naris was exceedingly large. A remarkable departure from the generally narrow saurolophine aspect of this species is a general mediolateral expansion of the skull. This is evidenced by the broad exposure of the nasal on the skull roof, the shallow angle of inflection of the palatine vault, and the mediolateral extent of the symphysial process of the dentary. This expansion is here interpreted as dilation of the skull mediolaterally about the midline, resulting in greater separation of paired cranial elements. Dilation of the cranium appears to be a morphogenetic accommodation to the modification of the anterior dentary.

Additional Hadrosaurid elements were recovered at Rattlesnake Mountain from the same stratigraphical interval as the holotype of Aquilarhinus palimentus, some bones within a short distance of the collection site of the holotype. Although this material might pertain to Aquilarhinus palimentus, none of these isolated bones exhibit diagnostic features that would allow certain attribution. This material includes a braincase wall, a parietal bone, a frontal, a postorbital, a scapula, a humerus, a pubis, an ilium, a femur, and a tibia.

With reconstructed quadrate and skull lengths of 26 cm and 57 cm, respectively, TMM 42452-1 is a relatively small Hadrosaurid individual. For example, compared to other Hadrosaurids from the same time period, the skull of TMM 42452-1 is estimated to be only 50% the length of the skull of Gryposaurus latidens, and 65% of the length of the skulls of Acristavus gagslarsoni and Probrachylophosaurus bergei. By analogy with Gryposaurus spp. it could be assumed that the nasal arch of Aquilarhinus palimentus would become more prominent with growth. However, it is also possible that the nasal arch of Aquilarhinus palimentus experienced a different allometric growth trajectory than that of Gryposaurus spp. Therefore, Prieto-M arquez et al. are uncertain at this juncture regarding the degree of maturity of TMM 42452-1, pending the discovery of additional specimens.

Reconstruction of the skull and mandible of Aquilarhinus palimentus. Areas coloured in brown indicate bones belonging to specimen TMM 42452-1. Prieto-M arquez et al. (2019).

The presence of a gentle arch on the dorsal surface of the nasals of Aquilarhinus palimentus is reminiscent of the nasal crest in species of the Saurolophine Gryposaurus. Gryposaurus ranges from the early Campanian to possibly the late Maastrichtian and is distributed from southern Canada to south-western Texas Notably, Gryposaurus latidens, from lower Campanian strata of the Two Medicine Formation of Montana, represents one of the oldest known Hadrosaurids, with an estimated age of 80 million years. A nasal arch is also present in Rhinorex condrupus, a sister taxon to Gryposaurus spp. from the Neslen Formation of eastern Utah, in late Campanian strata dated to 75–74.5 million years ago. Despite sharing an arcuate dorsal profile of the nasal, Aquilarhinus palimentus is clearly different from Rhinorex condrupus and Gryposaurus spp. The external bony naris (at least the dorsal extent) of Gryposaurus spp. and Rhinorex condrupus is significantly narrower anteroposteriorly than that of Aquilarhinus palimentus. The maxilla of Gryposaurus shows a jugal tubercle instead of a jugal process, and its premaxillary shelf is steeply inclined at least 40° relative to the tooth row compared to the less inclined shelf of quilarhinus palimentus which is inclined at 30 °. Finally, the anterior process of the jugal of Gryposaurus and Rhinorex condrupus is substantially deeper with a relatively short anterior apex, compared to the shallow process and long apex of Aquilarhinus palimentus.

Right nasal of the holotype specimen (TMM 42452-1) of Aquilarhinus palimentus. (A) Lateral view; (B) interpretive line drawing of the lateral view; (C), medial view; (D), interpretive line drawing of the medial view. Dark grey indicates reconstruction, cross hatching indicates broken surfaces, open circles represent concretionary matrix. Prieto-M arquez et al. (2019).

Naashoibitosaurus ostromi is a Kritosaurin Saurolophine originally described on the basis of a skull and fragmentary postcranium. The nasals display a low but acute arch. Unlike Aquilarhinus palimentus, however, the nasal crest of Naashoibitosaurus ostromi lies farther posterodorsally relative to the posterior margin of the external bony naris. Most notably, the posterodorsal margin of the external bony naris is very narrow in Naashoibitosaurus ostromi, less than half the width of the broad sub-circular margin enclosed by the nasal of Aquilarhinus palimentus. In addition, a deep circumnarial fossa excavates the lateral surface of the nasal surrounding the external bony naris of Naashoibitosaurus ostromi, whereas the fossa is distinctly shallower in Aquilarhinus palimentus. As in other Hadrosaurids, but unlike Aquilarhinus palimentus, the maxilla of Naashoibitosaurus ostromi shows a dorsal jugal tubercle rather than a jugal process and the occlusal plane displays a maximum of two functional teeth. The dorsal surface of the premaxillary shelf is concave and substantially narrower, about half the width of that in Aquilarhinus palimentus. Similarly, the palatal process of Naashoibitosaurus ostromi is much shallower, about half the depth seen in Aquilarhinus palimentus.

Although the premaxillae of Aquilarhinus palimentus were not recovered, there is no indication that the bizarre mandibular symphysial configuration in this species was related to the circumnarial structure, nor is it likely to be related to any part of the vocal, thermoregulatory, defensive or other physiological behavioural systems functionally linked to the rostrum. Prieto-M arquez et al. consider it more likely that the autapomorphic dentary symphysis is linked to restructuring of the rostrum for a unique feeding strategy. The projection and curvature of the symphysial processes of the dentary, nearly horizontal palatines and wide nasals all suggest that this animal was broad snouted, if not simply broad headed, also suggesting trophic adaptation. The dentaries and their symphysial processes would have met in a ‘W’-shaped section anteriorly. Assuming the predentary retained its ancestral relationships to the features of the anterior dentary, it would have been shaped like two trowels laid side to side. The raised symphysis might have led to a raised ridge that passed between the concave predentary fossae along the midline, much like the strengthening ridge leading from the handle onto the blade of a spade or shovel. The anterior extension of the symphysial processes, and the general proportions of the dentaries, suggests that the predentary may have been relatively long.

The hypothesized shovel-shaped ‘bill’ and widening of the skull in Aquilarhinus palimentus may have been adapted for shovelling out and scooping up vegetation. The central reinforcing ridge developed from the dentary symphysis would produce two strong arches in cross section to resist the strain of pushing through sediment or vegetation. The dentary was straightened relative to that of ancestral Hadrosaurids, likely in order to bring the predentary into alignment with the axis of the mandibles, reducing bending stress along the length of the bone and keeping material from falling out of the predentary. The widening of the mandible, and corresponding widening of the cranium, produced a wider ‘scoop’.

The adaptations of this animal, as interpreted by Prieto-M arquez et al., bring to mind those of Gomphotherid Proboscideans, Sirenians, Hippopotamus, the South American Pyrotheres and, especially, Desmostylians. These groups are or were relatively large-bodied herbivorous Mammals, many either semiaquatic or closely related to aquatic forms. Moreover, these taxa share narial specializations, as also occur in Hadrosaurids. These analogies suggest that Aquilarhinus palimentus may have been a paralic, possibly semiaquatic species specialised for digging in loose wet sediment. This habitus is consistent with the facies interpretation of the strata in which the type specimen was found.

Trophic specialization does not seem exceptionally common among Hadrosaurids; some non-Hadrosaurids (e.g. Protohadros byrdi) and the Lambeosaurine Angulomastacator daviesi have strongly ventrally deflected rostra, but a direct connection to feeding habits has not been proposed. Some palaeontologists have have proposed trophic specializations based on the diameter of the premaxillary ‘beak’. While this is understandable, Prieto-M arquez et al. feel that until the morphogenetic relationship between the beak and the circumnarial fossa can be explored in detail, it is wisest to consider this tentative. The conformation of the dentary symphysis in Aquilarhinus palimentus is so far the most likely candidate for a clear trophic specialisation among Hadrosaurids.

Ancestral state reconstructions for the presence of an osseous cranial crest (in its simplest form, an elevation of the skull roof above the sub-horizontal ancestral cranial profile) indicate that the most recent common ancestor of the clade including Saurolophidae and the Aquilarhinus-Latirhinus lineage probably sported a crest. The presence of a cranial crest was also likely ancestral for Saurolophids as a whole, including both Lambeosaurines and Saurolophines. Therefore, the ‘solid crests’ of Saurolophines and the ‘hollow crests’ of Lambeosaurines are most likely homologous. It would, then, be less appropriate to say that the crest has evolved several times among Saurolophids, and more reasonable to suggest that it is the conformation of the crest, not the presence or absence of a crest, which has been most labile among Hadrosaurids.

Both parsimony and maximum likelihood optimization methods support the hypothesis that the arched nasals of Aquilarhinus palimentus did not evolve independently from those of derived Hadrosaurids such as Gryposaurus and other Kritosaurins that are deeply nested within Saurolophinae but are in fact homologous. This may indicate that the arched nasal crest is the ancestral conformation of the crest, and all other Hadrosaurid crests are ultimately derived from the arched nasal crest.

The lack of sufficient cranial material in Hadrosaurus foulkii prevents ascertaining whether crests were ancestral for Hadrosauridae. The unadorned skull of another non-Saurolophid Hadrosaurid, Eotrachodon orientalis suggests tentatively that the earliest Hadrosaurids lacked supracranial crests. On the other hand, osseous crests must have been lost at least twice within Saurolophinae (Acristavus gagslarsoni and Edmontosaurini) and might have been lost in Eotrachodon orientalis as well. So far, there is only evidence that enclosure of the nasal passages to form a ‘hollow’ crest occurred once, in Lambeosaurines. However, this must have happened quite early in their evolution.

Aquilarhinus palimentus represents a new genus and species of Hadrosaurid from the early Campanian of south-western Texas. This taxon is characterised by several autapomorphies of the facial skeleton, the most remarkable of which consists of a dentary symphysis that is reflected dorsally as well as anteromedially projected. The latter condition, along with evidence of a relatively broad skull, suggest that this Hadrosaurid may have fed by shovelling material, possibly soft water plants.

This new species is one of the oldest Hadrosaurids and one of the few non-Saurolophid Hadrosaurids known to date, forming a group of ‘broad-nosed’ forms with Latirhinus uitstlani that branched off before the major clades Saurolophinae (‘solid-crested’ and unadorned taxa) and Lambeosaurinae (‘hollow-crested’ taxa). This adds to the diversity of pre-Saurolophid taxa known to date, previously restricted to Hadrosaurus foulkii and Eotrachodon orientalis, and suggests the existence of a previously unrealized diversity of Hadrosaurid lineages that evolved prior to the main radiation of the clade.

Supracranial crests were possibly present ancestrally in non-Saurolophid Hadrosaurids, as well as in the common ancestor of Saurolophidae, Saurolophinae and Lambeosaurinae. Prieto-M arquez et al. find evidence in support of nasal arches as the ancestral crest morphology, from which other derived types of supracranial ornaments evolved within Saurolophid Hadrosaurids.

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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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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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