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- ItemCranial and postcranial morphology of the insectivoran-grade mammals Hsiangolestes and Naranius (Mammalia, Eutheria) : with analyses of their phylogenetic relationships (Bulletin of the American Museum of Natural History, no. 463)(American Museum of Natural History., 2023-06-26) Ting, Suyin; Wang , Xiaoming (Paleontologist); Meng, Jin (Paleontologist)Early Cenozoic “insectivorans” possess some of the most primitive morphologies among eutherian mammals. Studies of these archaic mammals offer insights into the early diversifications of basal eutherians. Despite such importance, early fossil “insectivorans” from Asia are poorly known due to a scarcity of fossil remains, which often consist only of fragmentary jaws and teeth. Discoveries of remarkably well-preserved fossil “insectivorans”, including complete skulls and articulated postcranial skeletons, from the early Eocene Hengyang Basin in south-central Hunan Province, China, offer a rare opportunity to thoroughly study two taxa belonging to different families. Fine-grained red beds from Hengyang Basin preserve extraordinary fossils with morphological structures rarely seen elsewhere. Thin sections of a skull of Hsiangolestes youngi Zheng and Huang, 1984, for example, reveal the extremely delicate nasal and maxillary turbinates, which, as far as we are aware, are the first known from fossils of this age. We thus take this opportunity to document in detail the cranial and dental morphology, as well as postcranial skeletons, of the Hengyang “insectivorans”. In this monograph, we describe several complete skulls and serial sections of a skull, as well as many partial skulls, mandibles, and postcranial skeletons of Hsiangolestes youngi, an Asian early Eocene insectivoran-grade mammal. We also report a new species of Naranius Russell and Dashzeveg, 1986—N. hengdongensis—an Asian early Eocene cimolestid and describe its well-preserved skulls and mandibles. Hsiangolestes is endemic to Asia. It is currently known only from the earliest Eocene Lingcha Formation, Hengyang Basin, Hunan Province, China. Naranius closely resembles Cimolestes Marsh, 1889, the type genus of the family Cimolestidae. It is mainly distributed in Asia and known from the earliest Eocene deposits in the Bumban Member of the Naran Bulak Formation, Nemegt Basin, of Mongolia, and the Lingcha Formation, Hengyang Basin, Hunan Province, China. The only record of Naranius reported outside of Asia is N. americanus from the early Wasatchian Red Hot Local Fauna, Mississippi, United States. Using PAUP and TNT search algorithms, we place these Hengyang taxa within phylogenetic context of other fossil “insectivorans” from the Mesozoic and early Cenozoic of Asia together with some well-known Holarctic taxa. A phylogenetic analysis of 290 cranial and dental characters from 36 fossil and modern insectivoran-grade taxa is presented, focusing on new materials of Hsiangolestes youngi and Naranius hengdongensis. Based on the results of our phylogenetic analyses, we propose that (1) Hsiangolestes, Prosarcodon, Sarcodon, and Sinosinopa, form a monophyletic group, for which we propose the family name Sarcodontidae; (2) the family Cimolestidae should be restricted to Naranius and Cimolestes, which are sister taxa; (3) the systematic position of Naranius americanus is uncertain; and (4) the family Micropternodontidae should be restricted to Micropternodus and its allies in North America.
- ItemTransverse canal foramen and pericarotid venous network in Metatheria and other mammals (Bulletin of the American Museum of Natural History, no. 462)(American Museum of Natural History., 2023-06-21) MacPhee, R. D. E.; Gaillard, Charlène; Forasiepi, Analía M.; Sulser, R. BenjaminAlthough few nondental features of the osteocranium consistently discriminate marsupials from placentals, the transverse canal foramen (TCF) has been repeatedly offered as a potential synapomorphy of crown-group Marsupialia and their closest allies. To explore this contention appropriately, the TCF needs to be evaluated in relation to the morphofunctional complex of which it is a part, something never previously undertaken in a systematic fashion. This complex, here defined as the pericarotid venous network (PCVN), is assessed using osteological, histological, and ontogenetic information. Although the TCF is usually thought of as a marsupial attribute, some living placentals also express it. What do these clades actually share in regard to this feature, and how do they differ? Our leading hypothesis is that the chief components of the PCVN begin development in the same way in both Marsupialia and Placentalia, but they follow different ontogenetic trajectories in terms of persistence, size, and connections with other elements of the cephalic venous vasculature. Similarities include shared presence of specific emissary and emissarylike veins in the mesocranial region that connect part of the endocranial dural vasculature (cavernous sinus or CS) to the systemic circulation (external and internal jugular veins plus the cerebrospinal venous system). In marsupials the principal pericarotid vessels are the transverse canal vein (TCV) and internal carotid vein (ICV). These veins almost always attain relatively large size during marsupial ontogeny. By contrast, in most placentals their apparent homologs (among others, emissary vein of the sphenoidal foramen and internal carotid venous plexus) evidently slow down or terminate their growth relatively early, and for this reason they play only a proportionally minor role in cephalic drainage in later life. In both clades, these vessels (informally grouped with others in the same region as pericarotid mesocranial distributaries, or PMDs) play a variable role in draining the CS in conjunction with the much larger petrosal sinuses. A pneumatic space within the basisphenoid—called the sphenoid sinus in placentals, transverse basisphenoid sinus (TBS) in marsupials—communicates with PCVN vasculature and should be considered an integral part of the network. The TBS contains red marrow tissues that are active centers of extramedullary hematopoiesis in young stages of some species, although how widespread this function may be in marsupial clades is not yet known. Previous explorations of the marsupial PCVN have been largely limited to determining whether, in any given taxon, a continuous passageway linking the right and left TCFs could be demonstrated running through the basisphenoid (“intramural” condition). It has long been known that a number of species apparently lack this particular passageway, and that the TCFs instead open into the braincase (“endocranial” condition). Puzzlingly, some species appear to have both passageways, others one or the other, and a few none at all, thus inviting questions about their equivalency and the circumstances under which the CS is actually drained by the TCV. Morphologically, these uncertainties can be resolved by viewing the full TCV as a tripartite entity, consisting of a trunk and rostral and caudal branches. The trunk, or the part that leaves the TCF for the external jugular system, receives the rostral and caudal branches, if both are present, within the body of the basisphenoid. The rostral or intramural branch has little or no direct communication with the endocranium in most investigated species. By contrast, the caudal or endocranial branch is an ordinary emissarium, in that it connects a part of the endocranial system of dural veins with the extracranial circulation. Determining branch routing alone does not adequately capture the scale of morphological variety and function encountered in marsupial PCVN organization. We distinguish five patterns of association between TCVs and other PCVN components. These patterns, based on both histological and osteological criteria, are defined as follows: (1) Simple: only rostral passageway present, caudal passageway absent or reduced to a thread; rostral branch veins form midline confluence within TBS in advance of hypophysis; minimal interaction with CS and its distributaries; rostral and caudal portions of TBS discontinuous. (2) Complex: mostly as in (1), except both rostral and caudal branches present and functional; caudal branches communicate with CS/ICV and do not form a confluence; TBS more extensive. (3) Compound: mostly as in (2), except TBS greatly expanded, incorporating most of rostral branch canals, which are correspondingly short. (4) Hybrid: differs from others in that only the pathways for enlarged caudal branches are significant; they originate from the CS/ICV caudal to the position of the hypophysis; rostral branches absent or highly reduced. (5) Indeterminate: transverse foramina, canals, and branches absent or unidentifiable as such, presumably due to vascular involution early in ontogeny. In light of TCV composition, the trunk of the TCV can be considered a mixed-origin vein, maximally receiving both a quasisystemic or emissarylike vessel (rostral branch) that does not originate from endocranial dural vessels, and a true emissarial vessel (caudal branch) that does. Some extant geomyoid rodents and strepsirrhine primates exhibit enlarged venous structures in the mesocranial region; these are briefly surveyed for comparative purposes, but resemblances to conditions in marsupials are superficial and unmistakably interpretable as convergences. Members of the extinct marsupial sister group Sparassodonta sometimes lack detectable TCFs, as do other non-marsupial metatherians in the fossil record. Evidence for the transverse canal and other PCVN components in other therians is briefly outlined. In summary, the development of mesocranial vasculature as outlined in this paper is hypothesized to be basal for therians, but Marsupialia and Placentalia radically differ in the end expression of PMDs in the adult stage. In prenatal stages of both clades, initial differentiation of these distributaries is presumably similar, but, compared to marsupials, in almost all placental groups these vessels are retained in an undeveloped or neotenic state. By contrast, enhanced expression of the TCV trunk and its branches seems to be a genuine novelty characterizing Marsupialia, although one probably present in some other metatherian groups. Accordingly, the transverse foramen, canal, and related features are probably best regarded as an innovation occurring in the marsupial stem, not a synapomorphy of the crown group as previously suggested by some authors.
- ItemSystematic revision of Thomasomys cinereus (Rodentia: Cricetidae: Sigmodontinae) from northern Peru and southern Ecuador, with descriptions of three new species (Bulletin of the American Museum of Natural History, no. 461)(American Museum of Natural History., 2023-06-21) Pacheco Torres, Víctor R. (Víctor Rául); Ruelas, DennisseThomasomys cinereus is the type species of Thomasomys, type genus of the sigmodontine tribe Thomasomyini. As currently recognized, Thomasomys includes 48 species, all of which are endemic to humid montane or premontane forests in the tropical Andes. Although it has been suggested that T. cinereus is a species complex, this hypothesis has yet to be critically evaluated. Herein we provide a revision of the species based on a qualitative assessment of external, craniodental, and soft morphological traits; morphometric analyses; a phylogenetic analysis based on cytochrome b gene sequences; species delimitation methods; and first-hand examination of type material. Our analyses of genetic data recovered four distinct clades within T. cinereus, one corresponding to T. cinereus sensu stricto (restricted to the montane forests delimited by the Río Marañón, Río Huancabamba, and Río Tablachaca in Cajamarca department, Peru) and three new species: Thomasomys lojapiuranus, sp. nov., from the montane forests of Piura department, Peru, and Loja province, Ecuador; T. shallqukucha, sp. nov., restricted to the Kañaris montane forests in the Peruvian department of Lambayeque; and T. pagaibambensis, sp. nov., restricted to the montane forests of Pagaibamba in Cajamarca department, Peru. These species can be distinguished by several discrete morphological traits of the skull, dentition, mandible, stomach, palatal rugae, and glans penis. Genetic distances among these taxa range from 5.06%–7.65% at the cytochrome b locus, and delimitation analyses based on cytochrome b sequence data support their recognition as distinct species. Our results suggest the existence of previously unsuspected dispersal barriers in the Andes of northern Peru, and they confirm that the Río Marañón is a formidable barrier that limits the distribution of species of Thomasomys as well as other sigmodontine rodents.
- ItemGeneric revisions of the Scopaeina and the Sphaeronina (Coleoptera: Staphylinidae: Paederinae: Lathrobiini) (Bulletin of the American Museum of Natural History, no. 460)(American Museum of Natural History., 2023-06-21) Herman, Lee H.The generic classifications of the paederine subtribes Scopaeina Mulsant and Rey, 1878, and Sphaeronina Casey, 1905, are revised. Sphaeronina, revised status, is resurrected from synonymy. Keys to the included genera of both subtribes are included. Newly discovered characters in both subtribes are discussed and illustrated. The Scopaeina now includes Scopaeus, Hyperscopaeus, Micranops, Orus, and Trisunius. The account for each genus includes its diagnostic characters, a description, summary of the general distribution, and list of the included species and specimens examined. Scopaeus Erichson, 1839, has a revised definition and is now restricted to species that have not only a constricted neck and a trichobothrium adjacent to and at about the middorsal margin of the eye, but also a metathoracic/mesofemoral stridulum comprised of a lateral, metaventral file and mesofemoral plectral ridges, slender, apically acute, metakatepisternal processes, and a middorsally fused median lobe of the aedeagus. The stridulum, redefined herein as a file and plectrum that when rubbed together produce stridulation in insects. The metaventral file and mesofemoral plectral ridges of Scopaeus, is, heretofore, unknown in the Staphylinidae or perhaps, even the Coleoptera. Variations of the stridulum and metakatepisternal processes are illustrated and described for each species group. Five genus-group names in the Western Hemisphere, Scopaeomerus Sharp, 1886, and Euscopaeus Sharp, 1886, are new synonyms of Scopaeus; Scopaeodera Casey, 1886, Scopaeoma Casey, 1905, and Scopaeopsis Casey, 1905, are revised status junior synonyms of Scopaeus. The species in those generic groups are now included in species groups of Scopaeus. Hyperscopaeus Coiffait, 1984, new status, is elevated to genus from subgeneric status in Scopaeus. Trisunius Assing, 2011, new subtribal assignment, is moved from the Medonina to the Scopaeina. Typhloscopaeus Jarrige, 1951, incertae sedis, formerly a subgenus of Scopaeus, is of unknown placement, but the species and generic names are retained in Scopaeus awaiting study of the type. Orus cervicula Casey, 1905, revised combination, is returned to Orus from Scopaeus. Orus femoralis (Sharp, 1887), new combination, is transferred from Scopaeus. There are now three named species of Orus with narrow necks. Scopaeus chiriquensis (Sharp, 1886), S. guatemalensis (Sharp, 1886), S. obscurus (Sharp, 1886), and S. palmatus (Sharp, 1886), new combinations, are transferred to Scopaeus from Scopaeomerus. Medon mexicanus (Bernhauer, 1910), new combination, is transferred to Medon from Scopaeomerus. Scopaeus crassitarsis (Sharp, 1886), S. gracilicornis (Sharp, 1886), S. impar (Bierig, 1935), new combinations, are transferred to Scopaeus from Euscopaeus.The following names are transferred from Scopaeus to Hyperscopaeus as new combinations: Hyperscopaeus admixtus (Fagel, 1973), H. albertvillensis (Fagel, 1973), H. allardianus (Fagel, 1973), H. andrewesi (Cameron, 1931), H. angolanus (Fagel, 1973), H. bamaniaensis (Fagel, 1973), H. borneensis (Cameron, 1941), H. bredoanus (Fagel, 1973), H. calidus (Bernhauer, 1932), H. confusoides (Fagel, 1973), H. confusus (Fagel, 1973), H. consimilis (Fagel, 1973), H. convexiceps (Bernhauer, 1932), H. corpulentus (Fagel, 1973), H. decelleanus (Fagel, 1973), H. dolosus (Fagel, 1973), H. endrodyanus (Fagel, 1973), H. errans (Fagel, 1973), H. erraticus (Fagel, 1973), H. fageli (Levasseur, 1981), H. fallaciosus (Fagel, 1973), H. filicornis (Fagel, 1973), H. flavidulus (Fagel, 1973), H. flavocastaneus (Lea, 1923), H. fluviatilis (Fagel, 1973), H. fossiceps (Eppelsheim, 1885), H. fuliginosus (Fagel, 1973), H. fulvescens (Motschulsky, 1858), H. fusculus (Motschulsky, 1858), H. gigantulus (Bernhauer, 1929), H. girardianus (Fagel, 1973), H. hova (Fauvel, 1905), H. hulstaertianus (Fagel, 1973), H. intermixtus (Fagel, 1973), H. kaszabianus (Fagel, 1973), H. katanganus (Fagel, 1973), H. kivuanus (Fagel, 1973), H. lamtoensis (Fagel, 1973), H. leleupianus (Fagel, 1973), H. leopoldvillensis (Fagel, 1973), H. lescuyeri (Delaunay, Coache, and Rainon, 2019), H. levasseuri (Lundgren, 1982), H. longiusculus (Fagel, 1973), H. machadoanus (Fagel, 1973), H. major (Eppelsheim, 1885), H. methneri (Bernhauer, 1932), H. minutulus (Fagel, 1973), H. mulongoensis (Fagel, 1973), H. nitidiceps (Fagel, 1973), H. nitidicollis (Fagel, 1973), H. opacicollis (Bernhauer, 1942), H. overlaetianus (Fagel, 1973), H. parvicornis (Fauvel, 1900), H. procerus (Kraatz, 1859), H. pruinosulus (Eppelsheim, 1885), H. pseudomethneri (Fagel, 1973), H. puberulus (Kraatz, 1859), H. reduncus (Fagel, 1973), H. ripicola (Fagel, 1973), H. rubricollis (Fagel, 1973), H. rubrotestaceus (Kraatz, 1859), H. ruguliceps (Fagel, 1973), H. ruziziensis (Fagel, 1973), H. semifuscus (Kraatz, 1859), H. senegalensis (Fagel, 1973), H. seydeli (Cameron, 1952), H. simillimus (Fagel, 1973), H. simulator (Fagel, 1973), H. spathiferus (Coiffait, 1970), H. spinosophallatus (Frisch, 2012), H. subconfusus (Fagel, 1973), H. subprocerus (Coiffait, 1978), H. surdus (Fagel, 1973), H. suspectus (Fauvel, 1907), H. tchapembanus (Fagel, 1973), H. thoracicus (Motschulsky, 1858), H. tristis (Bernhauer, 1929), H. vagans (Fagel, 1973, and H. voltae (Fagel, 1973). Sphaeronina, revised status, is resurrected from synonymy and now includes Sphaeronum Sharp, 1876, Tripectenopus Lea, 1918, Typhloleleupius Fagel, 1964, and Coecoscopaeus Coiffait, 1982; the last three genera are new assignments to the subtribe. Sphaeronina is redefined by the presence of a hypopharyngeal peg, an enlarged protibial concavity with combs, a ventral denticle on the left mandible, and a groove on the outer edge of the mandibles; additional possible diagnostic characters are discussed. Sphaeronum, Tripectenopus, Typhloleleupius, and Coecoscopaeus are redescribed; the genera are found, respectively, in the American tropical and subtropical regions, Australia, southern Africa and perhaps Madagascar, and Tunisia. Few African and Australian were available for study. Scopaeodracus Scheerpeltz, 1935, is a new synonym of Tripectenopus. Tripectenopus handschini (Scheerpeltz, 1935), new combination, is transferred from Scopaeodracus; Tripectenopus australiae (Fauvel, 1878), T. microps (Lea, 1923), T. pectinatrix (Lea, 1923), and T. torrensensis (Blackburn, 1891), new combinations, are transferred from Domene.
- ItemComparative anatomy of the insect tracheal system, part 1. Introduction, apterygotes, Paleoptera, Polyneoptera (Bulletin of the American Museum of Natural History, no. 459)(American Museum of Natural History., 2023-03-10) Herhold, Hollister W.; Davis, Steven R., 1983-; DeGrey, Samuel P.; Grimaldi, David A.A broad comparative study of insect respiratory morphology is presented. Tracheae, epidermal invaginations extending into the body in branching networks of tubes, supply tissues with direct access to air for gas exchange. While previous tracheal studies focused on a handful of taxa and lacked in consistency, here a unified system of tracheal nomenclature is established using visualizations from micro-CT scanning of representatives from apterygotes, Paleoptera, and Polyneoptera, totaling 29 species, 29 genera, and 26 families in 13 insect orders. Three-dimensional visualizations of named tracheal branches establish robust assessments of homology and provide a framework for further studies across class Insecta. Patterns in respiratory architecture are presented along with a discussion of future investigations into phylogenetic and physiological questions.