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Nesting localities of extant birds and reptiles may provide taphonomic models for interpreting nesting sites of ancient archosaurs. Here we describe assemblages of nesting gulls (Larus delawarensis and L. californicus), American white pelicans (Pelecanus erythrorhynchos), and double-crested cormorants (Phalacrocorax auritus). Seventy nests yielded 2752 skeletal elements and 2308 eggshells. Most material was located inside the nest for gulls and consisted of osteologically mature gull bones and pelican eggshell. Pelican and cormorant nesting material were located outside the nest, with higher percentages of juvenile avian bone. Eggshell concave up and down ratios on the surface of gull nests compared closely to predated assemblages. Pelican and cormorant surface ratios were approximately 50:50, suggesting trampling by altricial young. Weathered bones in the subsurface of cormorant and pelican nests and layers of predated eggshell in gull nests suggest multi-year accumulations. The amount of material associated with the nests and the age of the nester's bones provides a means of distinguishing altricial and semi-precocial nesting sites. Nesting grounds for gulls with semi-precocial young yielded less skeletal material but a higher proportion of mature gull bones, whereas the large assemblages with altricial pelican and cormorant nests were dominated by prey items and their own young. [ABSTRACT FROM AUTHOR]

With abundant well-preserved clutches and several adult-clutch associations, oviraptorids provide some of the most detailed information on reproduction for dinosaurs. Here, we describe an oviraptorosaur closely associated with two eggs from the Upper Cretaceous Nanxiong Formation of Jiangxi Province, China, and discuss its implications for various reproductive hypotheses. The specimen consists of a partial skeleton (gastralia, pelvis, portions of both hind limbs, and tail), with one egg within the pelvic canal and the other just posterior to it, ventral to the anterior caudal vertebrae. Several geopetal features indicate that the individual came to rest on its left side, with the eggs likely extruded during buildup of abdominal gases during decomposition. Similarity of pubis, caudal vertebrae, and pes dimensions to recently described material from the formation, e.g., Tongtianlong and Jiangxisaurus, suggests oviraptorid affinities. The specimen provides additional association of elongatoolithid eggs and the oogenus Macroolithus with oviraptorosaurs and further evidence for monoautochronic ovulation, i.e., iterative laying of two eggs at daily or greater intervals. With each egg 36–48% the size predicted for a modern bird of the same adult mass, total egg production would be slightly lower to similar between this non-avian maniraptoran and Neornithes. Histological tissues and open neurocentral sutures indicate that this reproductively active individual was several years old but still growing at the time of death, a pattern observed in other non-avian maniraptorans. The complete absence of medullary bone in this egg-bearing individual may challenge the identification of this tissue in other dinosaurs more distantly related to birds. [ABSTRACT FROM AUTHOR]

Analysis of ontogenetic changes in long bone microstructure aid in vertebrate life history reconstructions. Specifically, osteohistological examination of common fauna can be used to infer growth strategies of biologically uncommon, threatened, or extinct vertebrates. Although nine-banded armadillo biology has been studied extensively, work on growth history is limited. Here we describe long bone microstructure in tibiae and femora of a limited ontogenetic series of nine- banded armadillos (Dasypus novemcinctus) to elucidate patterns of bone growth. The cortex of the smallest individual is composed of compacted coarse cancellous bone (CCCB) and woven tissue. Extensive cortical drift is driven by periosteal erosion and further compaction of trabeculae resulting in an increase in the amount of CCCB. The cortex of the largest specimens is primarily CCCB with thickened endosteal bone and thin outer cortices of lamellar and parallel-fibered tissue. The outer cortices of the largest individuals are interpreted as an external fundamental system (EFS) indicating a cessation of appositional bone growth corresponding to skeletal maturity (i.e. asymptotic or adult size). The EFS forms in femora prior to tibiae, indicating femoral growth rates begin decreasing earlier than tibial in D. novemcinctus. Growth trends in common fauna like the nine-banded armadillo can be used as a foundation for understanding life histories of related, but uncommon or extinct, species of cingulates. [ABSTRACT FROM AUTHOR]

Taphonomic and morphological evidence suggests that Oryctodromeus cubicularis, a basal ornithopod dinosaur from the mid-Cretaceous of Montana, constructed burrows by digging with its forelimbs. Reconstruction of the forelimb musculature of Oryctodromeus was carried out using the extant phylogenetic bracket method, with crocodilians and ratites as the extant analogues, aided by the presence of osteological correlates in Oryctodromeus and other ornithopods. Although reconstructions directly from the extant phylogenetic bracket are relatively conservative, the reconstruction elucidates several potential features related to burrowing. The prominent muscle groups used in burrowing in mammals are the deltoideus scapularis, teres major, latissimus dorsi, and triceps longus. In Oryctodromeus, the deltoideus scapularis, and equivocally the teres major, has broad origin on the strongly posteroventrally expanded distal scapular blade. Neither the origin of the deltoideus scapularis nor that of the teres major produces osteological correlates in extant taxa or Oryctodromeus; however, the ventrally expanded posterior scapular blade would have increased attachment area for the origin of these muscle groups. The presence of the latissimus dorsi is supported by the extant phylogenetic bracket but produces no osteological correlates in Oryctodromeus. The triceps longus originates posterior to the glenoid and inserts on the ulna. Due to the proximity of the triceps longus origin to the glenoid, the triceps longus likely did not provide strong muscle action. Because many mammals and reptiles produce burrows without any morphological specialization, the limited specializations of the deltoideus scapularis and potentially the teres major sufficiently support burrowing capabilities in Oryctodromeus. Citation for this article: Fearon, J. L. and D. J. Varricchio. 2016. Reconstruction of the forelimb musculature of the Cretaceous ornithopod dinosaur Oryctodromeus cubicularis: implications for digging. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1078341. [ABSTRACT FROM AUTHOR]