In order to assess general patterns of vertebrate hindbrain vasculature, we dissected a wide taxonomic range of latex‐injected specimens. Examinations of distantly‐related taxa including cyclostomes, elasmobranchs, actinopterygians and sarcopterygian tetrapods demonstrated a conserved suite of hindbrain vascular features including: 1) the origin and branching of cerebral (internal) carotids; 2) the ontogenetic origins of the basilar artery from paired precursors; and 3) the presence of a quasi‐segmental series of transverse basilar artery branches that extend circumferentially around the brainstem, giving off penetrating vessels. The major exception to this general pattern is found in teleosts, in which a series of midline segmental central arterial stems arise from the basilar artery and branch into intramural vascular trees within the sub‐ependymal zone of the hindbrain. The restriction of penetrating arteries to a series of dominant medial segmental stems in teleosts is derived relative to other vertebrates and may be part of a set of key innovations in this group. Phylogenetic analysis suggests that paired basilar arteries are primitive for jawed vertebrates, with unpaired basilars arising independently in chondrichthyes, teleosts and tetrapods. The hypothesized independent development of unpaired basilar arteries may represent convergence towards similar neurovascular functional designs. Given the highly dissimilar body plans and lifestyles of these groups, the overall conservation of hindbrain macrovasculature likely results from the primitive, shared similarity of embryonic brain development. Grant Funding Source: None

Remarks on Correlations and Implications of the Mandibular Structure and Diet in Some Seals(Mammalia, Phocidae). Koretsky, I. A., Rahmat, S. J., Peters, N. -Th e diverse representatives of Recent seals within the three extant subfamilies (Cystophorinae, Phocinae, Monachinae) of the family Phocidae exhibit dietary variations among species, feeding on invertebrates and a diversity of prey depending on the season and availability. To explain this variability, an introductory morphological examination of the mandibular structure of Recent seals from each subfamily was performed, focusing on: heights of the mandibular ramus and condyloid process; measurements of the masseteric fossa; and attachments of muscles of mastication. Aft er measuring the condyloid angles (the inclination of the condyloid process in relation to the axis of the alveolar row) among the examined species, a correlation between the size of the angle, function, and diet was recognized. Seals with a tall mandibular ramus and greater condyloid angle (Cystophorinae) feed on larger-sized prey, while seals with a shorter ramus and lesser condyloid angle feed on small (Monachinae) to medium-sized (Phocinae) prey, regardless of the overall size of the seal. Th is study focused on the mandibular morphology of some living and fossil representatives of Phocidae, providing an association between functional and ecological interpretations of modern seals in general and extrapolating this knowledge for fossil dietary preference.K e y w o r d s: Phocidae, mandibular ramus, carnivore, mammal, feeding, condyloid angle.Заметки по взаимосвязи челюстной структуры и диеты некоторых тюленей (Mammalia, Phocidae). Корецкая И. А., Рахмат С. Дж., Петерс Н. -Различные представители современных тюленей в рамках трёх сохранившихся подсемейств (Cystophorinae, Phocinae, Monachinae) семей-ства демонстрируют вариации в диете между видами, питаясь беспозвоночными и самой разноо-бразной добычей в зависимости от сезона и её доступности. Чтобы объяснить эту вариабельность, было выполнено вводное морфологическое исследование нижнечелюстной структуры современ-ных тюленей каждого подсемейства и уделено особое внимание: высоте челюстной ветви и бу-горков мыщелка; измерению жевательной ямки и прикреплению жевательных мышц. После из-мерения углов мыщелка (углу наклона бугорка мыщелка по отношению к оси альвеолярного ряда) среди исследованных видов была признана корреляция между размером угла, функцией и диетой. Тюлени с высокой ветвью нижней челюсти и большим углом мыщелка (Cystophorinae) питаются добычей большего размера, в то время как тюлени с более короткой ветвью и меньшим углом мыщелка питаются добычей небольших (Monachinae) и средних (Phocinae) размеров, независимо от общего размера тюленей. Это исследование было сосредоточено на морфологии нижней челю-сти некоторых живых и ископаемых представителей Phocidae, обеспечивая связь между функцио-нальными и экологическими интерпретациями современных тюленей в целом и экстраполяцией этих знаний на диетические предпочтения ископаемых тюленей.

Re-evaluation of Morphological Characters Questions Current Views of Pinniped Origins.Koretsky, I. A., Barnes, L. G., Rahmat, S. J. -Th e origin of pinnipeds has been a contentious issue, with opposite sides debating monophyly or diphyly. Th is review uses evidence from the fossil record, combined with comparative morphology, molecular and cytogenetic investigations to evaluate the evolutionary history and phylogenetic relationships of living and fossil otarioid and phocoid pinnipeds. Molecular investigations support a monophyletic origin of pinnipeds, but disregard vital morphological data. Likewise, morphological studies support diphyly, but overlook molecular analyses. Th is review will demonstrate that a monophyletic origin of pinnipeds should not be completely accepted, as is the current ideology, and a diphyletic origin remains viable due to morphological and paleobiological analyses. Critical examination of certain characters, used by supporters of pinniped monophyly, reveals diff erent polarities, variability, or simply convergence. Th e paleontological record and our morphological analysis of important characters supports a diphyletic origin of pinnipeds, with otarioids likely arising in the North Pacifi c from large, bear-like animals and phocids arising in the North Atlantic from smaller, otter-like ancestors. Although members of both groups are known by Late Oligocene time, each developed and invaded the aquatic environment separately from their much earlier, common arctoid ancestor. Th erefore, we treat the superfamily Otarioidea as being monophyletic, including the families Enaliarctidae, Otariidae (fur seals/sea lions), Desmatophocidae, and Odobenidae (walruses and extinct relatives), and the superfamily Phocoidea as monophyletic, including only the family Phocidae, with four subfamilies (Devinophocinae, Phocinae, Monachinae, and Cystophorinae).

The Family Phocidae includes four subfamilies (Phocinae, Monachinae, Cystophorinae, and Devinophocinae) consisting of mediumto large-sized mammals that possess distinctive adaptations to semi-aquatic life. In the Miocene of the Chesapeake Group, only two subfamilies of the Family Phocidae were identified: Phocinae and Monachinae. Leptophoca, a representative of the subfamily Phocinae, appears on the eastern shore of the North Atlantic around 16 million years ago. Recently, two new monachine species, the larger Terranectes magnus (n. gen., n. sp.) and the medium-sized T. parvus (n. sp.), were recorded in the Upper Miocene of the Chesapeake Group in the Eastover Formation (7.0–6.0 Ma) and St. Marys Formation (10.0-8.0 Ma). These two distinct subfamilies of seals indicate a well-marked divergence between phocines and monachines, much earlier than 18 million years ago, as previously suggested. The Eastover Formation was deposited in a shallow embayment that covered southern Maryland, the coastal plain of Virginia, and the northeastern corner of North Carolina. The geologically older St. Marys Formation represents a tide-influenced coastal environment, with low-salinity estuaries. There was a sharp temperature decrease in the Late Miocene, indicated by a shift to a cooler-water fish fauna during St. Marys time. The Eastover Formation reflects warmer waters with relatively strong currents, significant shoals, barriers, and varied depths. Fossil evidence of earlier seals suggests that phocids originated in the North Atlantic and otarioids in the North Pacific. True seals diverged from ancient Carnivora in the early Oligocene (or earlier) in the Paratethyan / Mediterranean Basins, spread widely during the Middle Miocene and crossed westward across the Atlantic Ocean, before dispersing in the eastern United States by the Early Pliocene.

First Record of Postcranial Bones in Devinophoca emryi (Carnivora, Phocidae, Devinophocinae). Rahmat, S. J., Koretsky, I. -Th e Devinophoca emryi material from the early Badenian, early Middle Miocene (16.26-14.89 Ma) presents mixed cranial and especially postcranial characters with the three extant phocid subfamilies (Cystophorinae, Monachinae and Phocinae), as well as unique postcranial characters not seen in any taxa. Th ese distinguishing characters (i. e. well-outlined, large oval facet on greater tubercle of humerus; broader width between the head and lesser tubercle of humerus; femoral proximal epiphysis larger than distal; thin innominate ilium that is excavated on ventral surface) demonstrate that this material belongs to a recently described species (D. emryi). During ecomorphotype analyses, fossil humerus and femur bones were directly associated with their corresponding mandible to reveal associations based on Recent morphological analogues. Strong correlation between ecomorphotypes and postcranial morphology supports placement of this material to D. emryi and not its sister taxon, D. claytoni. Th e previously described skull, mandible and teeth and postcranial bones described herein were discovered at the same locality during excavations at the base of the Malé Karpaty Mountains (Slovakia), at the junction of the Morava and Danube rivers. Th e geological age of D. emryi and the presence of mixed characters strongly suggest that this species was an early relative to the ancestor of seals, possibly being a terminal branch of the phocid tree. Th is material allows for emended diagnoses of the species, updated assessments of geographical distribution and provides further material for clarifi cation of controversial phylogenetic relationships in Phocidae.