Deltopectoral Crest Research Articles

Yuanjiawaornis viriosus, gen. et sp. nov., a large enantiornithine bird from the Lower Cretaceous of western Liaoning, China

Here we describe a new enantiornithine bird, Yuanjiawaornis viriosus gen. et sp. nov., based on a nearly complete, mostly articulated postcranial skeleton from the Lower Cretaceous Jiufotang Formation (120 Ma) of western Liaoning Province, northeastern China. It is similar in size to large bohaiornithids among the known Early Cretaceous enantiornithines; only Pengornis houi is larger. The semilunate carpal is incompletely fused to the metacarpals, suggesting that the holotype specimen was not fully mature at the time of death. The new specimen is distinguishable from other known enantiornithines by a unique combination of features including large body size, forelimb and hind limb subequal in length, a longitudinally grooved ventral surface of the synsacrum, robust and long transverse processes of the caudal-most sacral vertebra, a craniodorsally tapered acromion process of the scapula, a straight lateral margin of the coracoid, medially curved clavicular rami with tapered omal tips, a sternum that is oval in outline with slightly expanded distally caudolateral processes, a humeral head with a flat proximal surface, and a humerus with a deltopectoral crest that gradually decreases in height distally. A comparative analysis of some sacral features of basal birds including this taxon suggests that enantiornithines might have a uniquely shaped synsacrum, although more data is needed to confirm that hypothesis.

Cretornis hlavaci Frič, 1881 from the Upper Cretaceous of Czech Republic (Pterosauria, Azhdarchoidea)

Cretornis hlavaci Frič, 1881 from the Upper Cretaceous (Turonian) of Czech Republic is a valid taxon referred to Azhdarchoidea based on having a saddle-shaped humeral head, pneumatic foramen on proximal humerus present on anterior side and absent on posterior side, elongate deltopectoral crest with subparallel proximal and distal margins, pneumatic foramen absent on distal side of humerus, metacarpals I–III not articulated with carpus and displaced on anterodorsal side of wing metacarpal, and wing metacarpal much longer than humerus. Absence of a pneumatic foramen on posterior side of proximal humerus suggests attribution of Cretornis hlavaci to Neoazhdarchia. It has a unique construction of the distal ulna with a dorsal articulation surface placed distinctly proximal to the tuberculum shared only with the non-azhdarchid azhdarchoid Montanazhdarcho minor from the Campanian of North America. Cretornis hlavaci differs from the latter taxon by the structure of its humerus and distinctly longer wing metacarpal. It is more derived than “Tapejaridae” but shares with Azhdarchidae the deltopectoral crest of the humerus displaced distally from humeral head. Cretornis cannot be assigned to Azhdarchidae because of the oval cross section of the second wing phalanx. A unique rhombic outline of the distal humerus of Cretornis hlavaci is a possible autapomorphy for this taxon. Its wing span estimated as 1.5–1.6 m. This is the first taxon of non-azhdarchid pterosaurs known from the Upper Cretaceous of the Eastern Hemisphere.

New dinosaur remains from the Late Triassic of southern Brazil (Candelária Sequence, Hyperodapedon Assemblage Zone)

Pretto, F.A., Schultz, C.L., Langer, M.C. 4.02.2015. New dinosaur remains from the Late Triassic of southern Brazil (Candelária Sequence, Hyperodapedon Assemblage Zone). Alcheringa 39, xxx–xxx. ISSN 0311-5518The oldest unequivocal dinosaurian records come from Upper Triassic strata, mostly from Argentina and Brazil. Recent fieldwork in the Brazilian deposits of Ischigualastian age (late Carnian–earliest Norian) have resulted in the collection of a new specimen (UFRGS-PV-1240-T) identified as dinosaurian by the presence of a concave emargination on the ventral surface of the femoral head and a well-developed deltopectoral crest on the humerus, which extends for ca 40% of its estimated proximodistal length. Although fragmentary, the material increases the dinosaurian record from the Late Triassic of Brazil, which is still modest when compared with coeval Argentine strata. Additionally, UFRGS-PV-1240-T augments the dinosaurian diversity at the ‘Sítio Janner’ site, which was until now restricted to the sauropodomorph Pampadromaeus barberenai. The new specimen is larger than most early dinosaurians (except for herrerasaurids), implying that members of the group were already occupying niches otherwise explored by other larger-bodied taxa in the ‘Sítio Janner’ palaeofauna, and Late Triassic palaeoenvironments in general.Flávio A. Pretto [flavio_pretto@yahoo.com.br] and Cesar L. Schultz [cesar.schultz@ufrgs.br] Universidade Federal do Rio Grande do Sul, Instituto de Geociências, Setor de Paleovertebrados, Av. Bento Gonçalves, 9500—Bloco J, Prédio 43127, Campus do Vale, Agronomia−Porto Alegre, Rio Grande do Sul, Brazil, CEP 91540-000; Max C. Langer [mclanger@ffclrp.usp.br] Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Departamento de Biologia, Av. Bandeirantes, 3900, CEP 14040-901, Ribeirão Preto, São Paulo, Brazil.

Short note on a non-pterodactyloid pterosaur from Upper Jurassic deposits of Inner Mongolia, China

Daohugou is an important locality of the Jurassic Yanliao Biota, where only two pterosaurs have been described so far (Jeholopterus and Pterorhynchus). Here we report a new genus and species, Daohugoupterus delicatusgen. et sp. nov. (IVPP V12537), from this region, consisting of a partial skeleton with soft tissue. The skull is laterally compressed, differing from Jeholopterus. The antorbital fenestra is larger than in Pterorhynchus. The upper temporal fenestra is unusually small. The short cervical vertebrae bearing cervical ribs indicate that it is a non-pterodactyloid flying reptile. The sternal plate is triangular, being much wider than long. The deltopectoral crest of humerus is positioned proximally and does not extend further down the shaft, a typical feature of basal pterosaurs. Daohugoupterus also differs from the wukongopterids and scaphognathids from the Tiaojishan Formation at Linglongta, regarded to be about the same age as the Daohugou Bed. The new specimen increases the Jurassic non-pterodactyloid pterosaur diversity of the Yanliao Biota and is the smallest pterosaur from Daohugou area so far.

The postcranial skeleton of Vagaceratops irvinensis (Dinosauria, Ceratopsidae)

The postcranial skeleton of Vagaceratops (= Chasmosaurus) irvinensis (CMN 41357), lacking only the tail, most of the left front and left hind limbs, and portions of the pelvis, is preserved in articulation. It is one of the most complete, best articulated ceratopsid skeletons known. Both the manus and vertebral column exhibit conspicuous pathologies, possibly an indication of advanced age at the time of death. The vertebral column comprises a syncervical, six additional cervical vertebrae, and 12 dorsals. A partial synsacrum is represented by two dorsosacrals, four sacrals, two caudosacrals, and a partial third caudosacral centrum. The ribcage, although crushed, is nearly complete. The sternum is unusually wide compared with other ceratopsids. As in other chasmosaurines, the humerus bears a prominent deltopectoral crest that forms the anterior edge of the broad, rectangular proximal humeral expansion. The medial tuberosity is separated from the dorsal surface of the humerus by a distinct notch. The insertion for the latissimus dorsi is conspicuous. The deltopectoral crest extends a full half of the distance to the distal end of the humerus. Epipodials of the forelimb are relatively short compared to the corresponding propodial. The ulna has a long, distinctly triangular olecranon, broadly rounded anterolateral process, prominent medial process, and a deeply concave trochlear notch. The terminal phalanges on the fourth and fifth manual digits are relatively large, and unlike other ceratopsids have distinct distal ?articular facets. The fourth trochanter of the femur is relatively proximal in position. This study and other recent studies of ceratopsid postcrania suggest that potentially useful taxonomic variation is present in the number of dorsosacrals, size of the groove on the ventral surface of the sacrum, morphology of the last dorsal and dorsosacral ribs, morphology of the scapula and proximal expansion of the humerus, morphology of the ulna, ratio of humerus/epipodium, morphology of the fifth manual digit, and position of the fourth trochanter of the femur.

A new Hyperodapedon (Archosauromorpha, Rhynchosauria) from the Upper Triassic of India: implications for rhynchosaur phylogeny

AbstractA new species of the rhynchosaur genus Hyperodapedon, namely H. tikiensis, is described from well‐preserved skeletal elements that were collected from the Upper Triassic Tiki Formation of India. Hyperodapedon tikiensis is diagnosed on the basis of several cranial and postcranial features including longer than wide basipterygoid process, crest‐shaped maxillary cross section lateral to the main longitudinal groove, deeply excavated neural arches of mid‐dorsal vertebrae, long scapular blade, a pronounced deltopectoral crest, proximal humeral end much broader than distal end, iliac length greater than iliac height, equal pre‐ and postacetabular iliac lengths and circular femoral cross section. Two distinct morphotypes of the maxillary tooth plates can be discerned, which are attributed to ontogenetic variations. A maximum‐parsimony analysis was carried out to show that the order Rhynchosauria is characterized by nine cranial and one postcranial character states. The analysis reveals that Otischalkia elderae is invalid and the basal forms, Howesia and Mesosuchus, are closely related. The Mid‐Triassic genus Ammorhynchus is more derived and forms a sister group to the Late Triassic subfamily Hyperodapedontinae. Isalorhynchus and Teyumbaita are basal to the pandemic genus Hyperodapedon. Twenty‐four characters that are not homoplasious document major patterns of skeletal evolution in rhynchosaurs. From laterally oriented scapula and slender propodials, the postcranial skeleton evolved into a more robust form as is evident from nearly vertical scapula and increase in the robustness of the propodials. Shortening of the femur is noted in the derived Late Triassic forms as exemplified in Hyperodapedon gordoni, Hyperodapedon huxleyi and H. tikiensis.

Zby atlanticus, a new turiasaurian sauropod (Dinosauria, Eusauropoda) from the Late Jurassic of Portugal

ABSTRACTHere we describe a new partial sauropod skeleton from the late Kimmeridgian (Late Jurassic) of the Lourinhã Formation, central west Portugal. The closely associated specimen comprises a complete tooth (with root), a fragment of cervical neural arch, an anterior chevron, and an almost complete right pectoral girdle and forelimb. The new sauropod, Zby atlanticus, n. gen. et sp., can be diagnosed on the basis of four autapomorphies, including a prominent posteriorly projecting ridge on the humerus at the level of the deltopectoral crest. Nearly all anatomical features indicate that Zby is a non-neosauropod eusauropod. On the basis of several characters, including tooth morphology, extreme anteroposterior compression of the proximal end of the radius, and strong beveling of the lateral half of the distal end of the radius, Zby appears to be closely related to Turiasaurus riodevensis from approximately contemporaneous deposits in eastern Spain. However, these two genera can be distinguished from each other by a number of features pertaining to the forelimb. Whereas previously described Late Jurassic Portuguese sauropods show close relationships with taxa from the contemporaneous Morrison Formation of North America, it appears that turiasaurians were restricted to Europe. All adult sauropods recovered in the Late Jurassic of Portugal thus far are very large individuals: it is possible that the apparent absence of small- or medium-sized adult sauropods might be related to the occupation of lower-browsing niches by non-sauropods such as the long-necked stegosaur Miragaia longicollum.

Giant pterosaurs and the limits of animal flight (13.3)

Pterosaurs appear to have had a particular propensity for the evolution of large size compared with other flying animals: at least eight genera of pterosaurs included species with wingspans in excess of 4 meters. I present a launch constraints model that accurately predicts size trends in pterosaurs. Azhdarchid pterosaurs evolved a suite of traits associated with improved terrestrial ability and rapid launch, including an expanded and curved deltopectoral crest, expanded coracoid flange, elongate metacarpal IV, and a reinforced fourth metacarpal‐phalangeal joint. This pattern explains why the largest pterosaurs were members of the Azhdarchidae. Most other “giant” pterosaurs were marine, and may have been more constrained in size than azhdarchids as a result of water launching requirements. Large marine pterosaurs, such as anhanguerids, tended to possess an expanded scapula, reinforced scapular‐notarial joint, warped deltopectoral crest, exceptionally broad wing pivot joint, expanded posterior brachial musculature, and reduced hind limbs. These traits are predicted as specializations to water launching. Pneumaticity, forelimb hypertrophy, and quadrupedal launch, combined with selection for low energy loitering and/or extended range, explains the repeated evolution of large size in pterosaurs.

Evidence of titanosauriforms and rebbachisaurids (Dinosauria: Sauropoda) from the Early Cretaceous of Tunisia

Isolated sauropod remains including vertebrae and a humerus from the Aïn El Guettar Formation (Albian, Early Cretaceous) of Tunisia are described. Vertebrae include a slightly procoelous anterior caudal vertebra, amphicoelous middle caudal vertebrae, and strongly procoelous distal caudal vertebrae. The humerus has an anteroposteriorly compressed shaft, robust deltopectoral crest restricted laterally and prominent condyles bounding a distinct distal fossa. The morphological characters present in the specimens suggests that isolated remains can be referred to at least two distinct sauropod taxa.The anterior caudal vertebra is referred to Rebbachisauridae, whereas remaining caudal vertebrae show titanosauriform and titanosaurian derived features (anteriorly placed neural arches and, in the posterior vertebrae, distincly procoelous centra); finally, the humerus may pertain to a somphospondylian titanosauriform, perhaps the same taxon represented by the middle and posterior caudal vertebrae. This study introduces some of the oldest titanosauriform remains from Northern Africa and provides additional data on the stratigraphic and geographic distribution of this clade during the Early Cretaceous.

In utero foetal remains of the Cretaceous ichthyosaurian Platypterygius: ontogenetic implications for character state efficacy

AbstractIchthyosaurians provide some of the most famous examples of ‘live birth’ in the amniote fossil record based on spectacular complete skeletons of gravid females. Such remains facilitate direct comparisons between adult and foetal life stages, and thus have significant impact on phylogenetic hypotheses that require discrete character states to be ontogenetically uncoupled. This is especially true for Cretaceous ichthyosaurian taxa, the majority of which have been established using single specimens of assumed osteological maturity. Our assessment of in utero ichthyosaurian remains from the late Albian of Australia was therefore aimed at testing ontogenetic stability amongst key traits defining the most ubiquitous Cretaceous taxon: Platypterygius. Surprisingly, almost all of the salient features were identifiable in our sample of undoubtedly immature individuals. Indeed, only the proportions of the sclerotic ring, relative ossification and fusion of various basicranial elements, development of the axial skeleton, prominence of the deltopectoral crest and dorsal trochanter, and formation (but seemingly not number) of distal articular facets on the humerus were found to vary from larger-bodied members of the same species (P. australis). Ontogenetic continuity amongst the majority of other phylogenetically pertinent skeletal structures advocates their application for cladistic analyses, and suggests that many classic characters used to differentiate Platypterygius remain diagnostic irrespective of growth stage.

Capacity for the Cretaceous pterosaur Anhanguera to launch from water

Many large pterosaurs come from marine sediments. While the feeding ecology of large pterosaurs is contentious, it is likely that some species took food from the water surface. As a result, it is likely that some pterosaurs were forced into the water through stochastic events. Unless a water launch was possible, such events would presumably be lethal. Here I present the results of a quantitative and comparative morphological analysis of the large marine pterosaur Anhanguera santanae that suggest this animal could launch from water, without the assistance of wind or waves, using a form of quadrupedal takeoff. Initial escape from the water surface would use the most energy and could be accomplished with a net remaining acceleration of 17 m/s2, with an acceleration of up to 39 m/s2on the subsequent series of repeated propulsive bounds, which would have occurred as a series of “hops” across the water surface. While the capacity for such a behavior is not demonstration that such it was utilized, this species possessed a wide array of anatomical features that would make water launch both efficient and effective, and cannot be easily explained as adaptations to flight or walking: the expanded scapula, reinforced scapular‐notarial joint, warped deltopectoral crest, exceptionally broad MCIV‐PHIV wing finger joint, and expanded posterior brachial musculature. Funding provided by the Jurassic Foundation.

A new ornithopod (Dinosauria; Ornithischia) from Antarctica

A new ornithopod dinosaur from Antarctica, Trinisaura santamartaensis n. gen. et n. sp. is diagnosed by a unique combination of characters that includes a scapula with a spike-like acromial process with a strong and sharp lateral crest and longer than other ornithopods, a humerus with a rudimentary deltopectoral crest represented as a thickening on the anterolateral margin of the humerus, and shaft strongly bowed laterally, and an ischium gently curved along its entire length. The holotype specimen comprises vertebral and appendicular elements. The presence of axially elongate distal caudal vertebrae, pubis with long prepubic and postpubic processes, as well as a femur with a distinct anterior trochanter, pendant 4th trochanter and shallow anterior intercondylar groove constitute a combination of characters present in the Late Cretaceous Patagonian Gasparinisaura, Anabisetia and Talenkahuen. The materials were found on the surface enclosed in a hard sandstone concretion collected near the Santa Marta Cove, James Ross Island, from the lower levels of the Snow Hill Island Formation (Campanian). This is the first ornithopod taxon identified from this unit, and the second ornithischian dinosaur, after the ankylosaur Antarctopelta oliveroi. However, other ornithopod reports from nearby localities of James Ross and Vega islands in outcrops of the overlying Lopez de Bertodano Formation suggest that this clade was widely represented in the Campanian and Maastrichtian of the James Ross Basin, Antarctic continent.

Did Triadobatrachus Jump? Morphology and Evolution of the Anuran Forelimb in Relation to Locomotion in Early Salientians

The Lower Triassic amphibians Triadobatrachus massinoti and Czatkobatrachus polonicus are universally regarded as stem anurans. However, there is still uncertainty about whether or not they were capable of jumping like true anurans as their postcranial features have so far provided only equivocal evidence. Although previous work has concentrated on the anatomy of the hind limb, here we examine the anatomy of the forelimb, comparing stem and crown-group anurans to other amphibians. The forelimb and pectoral girdle of Triadobatrachus share several features with modern frogs, including a frog-like deltoid attachment of the scapula. Though the radius and ulna are unfused, the humerus is similar to those of modern anurans. The deltopectoral crest is slightly elongated and a lateral deflection of the ventral edge of the crest creates a concavity on the lateral face of the humerus. These features are uncommon in most tetrapod groups characterized by a sprawling stance but are typical of modern anurans, in which the anterior chest musculature is enlarged. Our findings indicate that the importance of the deltoid had increased relative to that of the pectoralis muscle in Triadobatrachus. Czatkobatrachus is somewhat less similar to modern jumping anurans in its deltopectoral crest and pectoral girdle. Most anurans extend the forelimbs forward during a jump and land on their forefeet, perhaps accounting for the enlargement of the deltoid and the orientation of the deltopectoral crest. This type of behavior during landing is not seen in Ascaphus and Leiopelma but several features of these two genera, such as the fusion of the radio-ulna, the forearm musculature, and the degree of medial rotation of the manus, indicate that their landing behavior may be derived rather than primitive. Overall, Triadobatrachus was certainly not as capable of long jumps as some modern anurans, yet its anatomy does suggest that jumping or hopping was part of its locomotor repertoire.

Ornithostoma sedgwicki – valid taxon of azhdarchoid pterosaurs

Ornithostoma sedgwicki Seeley, 1891 from the Lower Cretaceous (Albian) Cambridge Greensand of England is represented by edentulous jaw fragments, posterior skull fragment with the supraoccipital crest, and by several postcranial bones attributed previously to Lonchodectes. Ornithostoma is referred to the Azhdarchoidea based on a combination of derived characters (teeth absent, middle cervicals moderately elongated, pneumatic foramen on anterior side of humerus, large pneumatic foramen on posterior side of femur at greater trochanter) and plesiomorphic characters (deltopectoral crest not warped, femoral neck to shaft angle less than 145°). The structure of the supraoccipital crest and humerus resembles those in Tapejara, but Ornithostoma differs from that taxon by a strong median ridge on the occiput presumably associated with a more elongated rostrum. At least three taxa of basal azhdarchoids were present in the British Lower Cretaceous.

Nearly complete skeleton ofTetraclaenodon(Mammalia, Phenacodontidae) from the early Paleocene of New Mexico: morpho-functional analysis

We describe the relatively complete skeleton ofTetraclaenodonundoubtedly associated with its dentition, from the Torrejonian interval of the Nacimiento Formation in the San Juan Basin, New Mexico.Tetraclaenodonis the most primitive and oldest genus of the family Phenacodontidae and is very important for assessing the phylogenetic relationships of the family. The newly described skeleton belonged to a lightly built terrestrial mammal that could use trees for shelter. The structure of the ulna, manus, femur, crus, and pes corresponds to that of a typical terrestrial mammal, while morphological features such as the low greater tubercle of the humerus, long deltopectoral crest, pronounced lateral supracondylar crest, and hemispherical capitulum indicate some scansorial adaptations ofTetraclaenodon. The postcranial skeleton ofTetraclaenodondoes not exhibit the cursorial adaptations seen in later phenacodontids and early perissodactyls. Phylogenetic analysis did not recover monophyletic “Phenacodontidae”; instead, phenacodontids formed a series of sister taxa to the Altungulata clade.Tetraclaenodonis the basal-most member of the “Phenacodontidae” + Altungulata clade.

A morphometric approach to the specific separation of the humeri and femora of Dicraeosaurus from the Late Jurassic of Tendaguru,Tanzania

The two species of dicraeosaurid dinosaurs Dicraeosaurus, Dicraeosaurus hansemanni, and Dicraeosaurus sattleri, have been distinguished mainly by their differences in size and geological age, as they occur in different members of the Late Jurassic Tendaguru Formation of Tanzania. Linear and geometric morphometric measurements distinguish between the humeri and femora of both species. Linear measurements and Principal Component Analysis of Thin-plate Splines reveal strong differences in size and shape between their humeri and weak differences between their femora, also supported by a Discriminant Factor Analysis. Generally, the humerus and femur of D. hansemanni are slightly longer and more robust than those of D. sattleri. Further, the humerus is shorter in relation to the femur in D. sattleri, related to its more distally positioned deltopectoral crest, resulting in differences in its arc of movement and mechanical power. Thus, a morphological separation between the humeri and femora of D. hansemanni fro...

Cranial and appendicular ontogeny ofBactrosaurus johnsoni, a hadrosauroid dinosaur from the Late Cretaceous of northern China

Abstract: The juvenile anatomy of various cranial and appendicular elements of the hadrosauroid dinosaurBactrosaurus johnsoniis described in detail. Growth changes are documented from juvenile to adult stages for each skeletal element available. In the studied skull, ontogenetic trends consist of: development of features on the ventral surface of the frontal; reduction in the slope of the posteromedial process of the premaxilla; a posterior shift of the dorsal process of the maxilla; development of concavities on the medial surface of the prefrontal; increased robustness and development of the ventral flange of the jugal; decreased curvature of the long axis of the quadrate; increased ventral deflection of the dentary; and changes in the length/width proportions and depth of the anterior surface of the predentary. In the appendicular skeleton, the majority of ontogenetic variation from juvenile to adult occurs in the limb bones, including increased robustness of the deltopectoral crest of the humerus; relative shortening of the ulna; increased development of the fourth trochanter and mediolateral widening of the distal end of the femur; increased expansion of the cnemial crest of the tibia; and the increased prominence of articular protuberances and flanges of the metatarsals. A survey of the phylogenetically informative characters present inB. johnsoniindicates that several characters concerning the frontal, maxilla, jugal, quadrate, predentary, dentary, scapula, humerus and ilium are affected by ontogeny. Nevertheless, the majority of phylogenetic characters are not ontogenetically variable, suggesting that a substantial amount of the information provided by juvenile and subadult specimens for phylogenetic inference is reliable in basal hadrosauroids.

A new sauropodomorph dinosaur from the Early Jurassic of Patagonia and the origin and evolution of the sauropod-type sacrum.

BackgroundThe origin of sauropod dinosaurs is one of the major landmarks of dinosaur evolution but is still poorly understood. This drastic transformation involved major skeletal modifications, including a shift from the small and gracile condition of primitive sauropodomorphs to the gigantic and quadrupedal condition of sauropods. Recent findings in the Late Triassic–Early Jurassic of Gondwana provide critical evidence to understand the origin and early evolution of sauropods.Methodology/Principal FindingsA new sauropodomorph dinosaur, Leonerasaurus taquetrensis gen. et sp. nov., is described from the Las Leoneras Formation of Central Patagonia (Argentina). The new taxon is diagnosed by the presence of anterior unserrated teeth with a low spoon-shaped crown, amphicoelous and acamerate vertebral centra, four sacral vertebrae, and humeral deltopectoral crest low and medially deflected along its distal half. The phylogenetic analysis depicts Leonerasaurus as one of the closest outgroups of Sauropoda, being the sister taxon of a clade of large bodied taxa composed of Melanorosaurus and Sauropoda.Conclusions/SignificanceThe dental and postcranial anatomy of Leonerasaurus supports its close affinities with basal sauropods. Despite the small size and plesiomorphic skeletal anatomy of Leonerasaurus, the four vertebrae that compose its sacrum resemble that of the large-bodied primitive sauropods. This shows that the appearance of the sauropod-type of sacrum predated the marked increase in body size that characterizes the origins of sauropods, rejecting a causal explanation and evolutionary linkage between this sacral configuration and body size. Alternative phylogenetic placements of Leonerasaurus as a basal anchisaurian imply a convergent acquisition of the sauropod-type sacrum in the new small-bodied taxon, also rejecting an evolutionary dependence of sacral configuration and body size in sauropodomorphs. This and other recent discoveries are showing that the characteristic sauropod body plan evolved gradually, with a step-wise pattern of character appearance.

Appendicular skeleton of Simosuchus clarki (Crocodyliformes: Notosuchia) from the Late Cretaceous of Madagascar

ABSTRACT The notosuchian crocodyliform Simosuchus clarki from the Late Cretaceous of Madagascar, originally known from a single specimen preserving primarily the skull, lower jaw, and anterior postcranial skeleton, is now known from three additional partial skeletons that collectively preserve nearly the entire appendicular skeleton. Although typically crocodyliform in overall morphology, the appendicular skeleton of Simosuchus preserves a number of derived features of phylogenetic and functional significance. Notable features of the pectoral girdle and forelimb include an anteroposteriorly broad, tripartite scapular blade; a laterally directed scapular prominence; a proximally expanded humerus with a shallow deltopectoral crest; a distinct, semi-ellipsoidal glenohumeral condyle; a tightly articulating radius and ulna; and a relatively foreshortened manus with robust distal unguals. Notable features of the pelvic girdle and hind limb include a distinct, spur-like projection of the anterior process of the ischium; a femur with a distinctive anterior flange; and a relatively foreshortened pes. Generally, characteristics of the appendicular skeleton are consistent with a terrestrial lifestyle and provide insight into the behavior and locomotion of Simosuchus. The robust limb morphology observed in Simosuchus, together with expanded areas for insertion of pectoral and pelvic musculature in the proximal humerus and femur, is consistent with non-cursorial terrestrial locomotion in a relatively stout-bodied crocodyliform. Characteristics of the hind limb indicate a primarily semi-erect posture, in contrast to the erect posture inferred for other notosuchians.

A possible azhdarchid pterosaur from the Lower Cretaceous Qingshan Group of Laiyang, Shandong, China

ABSTRACT A new pterodactyloid pterosaur is identified from the Early Cretaceous Doushan Formaiton of Laiyang, Shandong Province, China, based on a fragmentary humerus. The humerus exhibits several diagnostic characters: deltopectoral crest is elongate and un-warped, its base is slightly displaced relative to the humeral shaft axis, and the crest is swollen terminally and ventrally displaced; humeral shaft is straight and thin-walled with a ‘D’-shaped cross-section. Based on these features, the specimen is referable to the superfamily Azhdarchoidea as Azhdarchidae indet. As the oldest known azhdarchid fossil, the specimen represents a significant stratigraphic range extension for the family. Other non-azhdarchid azhdarchoids such as tapejarids and chaoyangopterids are common in the Jiufotang Formation of western Liaoning, which possibly is equivalent to the Doushan Formation of Laiyang with an age of about 120 Ma. Consequently, the possible coexistence of these azhdarchoids lineages documents that the azhdarchids split from the main azhdarchoid clade occurred no later than the Early Cretaceous.