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Dissociated remains of the acanthodian Poracanthodes punctatus are described from Upper Silurian (Pridoli) limestones of the Roberts Mountains Formation at Pete Hanson Creek, Eureka County, Nevada. The vertebrate microremains in sample residues comprise scales, a dentigerous jaw bone fragment, and a fin spine fragment assigned to P. punctatus, plus one possible acanthothoracid placoderm scale. Some macroremains from the same locality are also assigned to P. punctatus. This taxon has been nominated as a zone fossil for the Silurian vertebrate biozonal scheme, and its presence has been recorded throughout the circum-Arctic region. Identification of the taxon in Nevada extends its known geographic range.
Fossilized Joffrichthys triangulpterus scales collected from an ancient lake site in the Paleocene Sentinel Butte Formation near Almont, North Dakota, provide an opportunity to estimate growth, natural mortality, and survival for this species. Based on 166 J. triangulpterus scales, fish ages ranged from zero through nine years old. Four scale-covered skeletons were also recovered and aged at zero, zero, one, and four years of life. Based on an age-frequency histogram, age groups zero, one, and two are clearly under-represented at the Almont site, suggesting they likely inhabited different areas of the lake system, perhaps due to habitat partitioning between juveniles and adults in the lake. Instantaneous natural mortality (M) determined from age-frequency data indicates the average annual mortality of age three and older J. triangulpterus was –0.456 (r2 = 0.958), which is similar to numerous extant fish mortality curves. A Von Bertalanffy growth curve (r2 = 0.977) indicates that growth of J. triangulpterus was rapid in the first three years of life, attaining over 70% of their adult size before reaching an asymptote in growth at age nine. The maximum body size attained by one individual of J. triangulpterus was estimated at 316 mm total length. The growth pattern and mortality rates exhibited in J. triangulpterus are generally similar to those of numerous extant fish taxa found in temperate latitudes.
A single specimen of the anterior portion of a small fish was collected from the Eocene Mahenge site of Tanzania in 1996. The specimen, preserved as part and counterpart natural mold, is identified as belonging to a characiform fish, although the presence of a Weberian apparatus has not been confirmed beyond doubt. Features of the bones, such as the prominent lateral ridge on the anterodorsal corner of the opercle, the fused postcleithra 2 3, and the lack of a dentary symphyseal hinge, indicate that the fish is related to the Citharinidae and Distichodontidae. The fossil cannot be included in any known genus, and is described here as a new genus and species, Eocitharinus macrognathus. The fossil record of characiforms includes few articulated skeletons, of which only one had been reported previously from Africa, described in the family Characidae (=Alestidae).
A new species of tilapiine cichlid, Oreochromis lorenzoi, is described from the late Miocene (Messinian) of central Italy. This species is represented by four articulated specimens and a caudal region of a fifth individual. Oreochromis lorenzoi, sp. nov. is the earliest confirmed representative of the genus Oreochromis, and it is the first European fossil cichlid. Oreochromis lorenzoi and additional examples from other fossil fishes provide evidence of faunal exchanges between Africa and the northern coasts of the Mediterranean during the Miocene. Paleoenvironmental implications are also discussed.
Lungfish of the tooth-plated lineage, both fossil and living, may be affected by alterations in the permanent tooth plates and associated jaw bones as they grow. In a few taxa, the unusual structures may be so common that they must be considered as normal for those species, or as a variation of the normal condition. In others the condition is rare, affecting only a few individuals. Variations, or anomalies, may appear in the growing tissues of the lungfish tooth plate at any time in the life cycle, although they usually appear early in development. Once the changes appear, they persist in the dentition. The altered structures include divided or intercalated ridges, short ridge anomaly, changes in the shape, number and position of cusps, pattern loss, and fused ridges or cusps. Criteria used to distinguish alteration from normal conditions are the incidence of the character in the population, the associated changes in the jaw bone, and the position of the altered structure in the tooth plate. The occurrence of similar changes across a wide range of different species suggests that they may have a genetic cause, especially when they are a rare occurrence in most taxa, but common enough to be a part of the normal variation in others. Prevalence of related anomalies throughout the history of the group suggests that dipnoans of the tooth-plated lineage are closely related, despite significant differences in morphology, microstructure, and function of the dentitions.
The cranial anatomy of Coloraderpeton brilli Vaughn and postcranial anatomy of Oestocephalus amphiuminus Cope are reconsidered in light of new ophiderpetontid material from Nýřany, Czech Republic. Coloraderpeton is distinct from Oestocephalus amphiuminus in having a quadrate region extended farther posterior of the occiput and a tabular restricted from the lateral temporal margin by the supratemporal. In contrast to the original description, Coloraderpeton, like all lepospondyls, lacks an intertemporal. Coloraderpeton has widely spaced teeth, which bring into question the utility of this character for separating Ophiderpeton from Oestocephalus. Coloraderpeton has multiple rows of teeth on its palatoquadrate, as opposed to the single row in Oestocephalus.
Oestocephalus has approximately 110 vertebrae. Vertebrae are not added posteriorly with growth, making vertebral counts of systematic significance in aïstopods. Transverse processes remain laterally directed throughout the column, unlike Phlegethontia, which has an anterior migration of the bases of the transverse processes, and an anterior inflection of the distal transverse processes that becomes more pronounced posteriorly. Ribs are present to about the 70th vertebra, leaving 40 rib-free caudal vertebrae, contrasting with the 100–160 rib-free caudal vertebrae of Phlegethontia. Ribs are “k-shaped,” with an anterior costal process and a long posterior process on either side of the tuberculum. No distinction can be made among any of the species from Linton, Ohio, Mazon Creek, Illinois, and Nýřany, Czech Republic, and so all are included within Oestocephalus amphiuminus. The exception is O. nanum from Newsham, Northumberland, which has reduced dorsal osteoderms. Preliminary phylogenetic analysis indicates that Ophiderpetontidae as previously understood are paraphyletic, and a new family, Oestocephalidae, is established to accommodate Oestocephalus and Coloraderpeton.
The “capitosaurs” from the Lower Triassic of Madagascar are revised. Benthosuchus madagascariensisLehman, 1961, and Wetlugasurus millotiLehman, 1961, are combined in the new combination Watsonisuchus madagascariensis on the basis of the most complete growth series among capitosaurians. A phylogenetic analysis showed that the genus Watsonisuchus is justified, although its species W. madagascariensis is not the most derived within the genus. The skull growth of W. madagascariensis clearly shows an allometric trend, but the fact that adults have more dermo-sensory grooves than juveniles suggests surprisingly that they may have become progressively more aquatic during growth. The ontogeny of W. madagascariensis is compared with that of other temnospondyls. Different longirostrine conditions are observed in Permian and Triassic stereospondylomorphs (archegosaurians and capitosaurians, respectively). They are interpreted as convergences rather than are a synapomorphy of the clade.
An accumulation of skeletons of the pre-dinosaur Silesaurus opolensis, gen. et sp. nov. is described from the Keuper (Late Triassic) claystone of Krasiejów in southern Poland. The strata are correlated with the late Carnian Lehrberg Beds and contain a diverse assemblage of tetrapods, including the phytosaur Paleorhinus, which in other regions of the world co-occurs with the oldest dinosaurs. A narrow pelvis with long pubes and the extensive development of laminae in the cervical vertebrae place S. opolensis close to the origin of the clade Dinosauria above Pseudolagosuchus, which agrees with its geological age. Among the advanced characters is the beak on the dentaries, and the relatively low tooth count. The teeth have low crowns and wear facets, which are suggestive of herbivory. The elongate, but weak, front limbs are probably a derived feature.
Indian and French dinosaur eggshell oospecies belonging to the oofamily Megaloolithidae are compared and, of the fourteen Megaloolithidae oospecies previously described from the Late Cretaceous of India, seven are considered junior synonyms. Comparisons between nine oospecies from India and France reveal four groupings which show similarities between megaloolithids of these countries: (1) Megaloolithus microtuberculata, M. cylindricus, and M. padiyalensis; (2) M. mamillare and M. jabalpurensis; (3) M. siruguei and M. khempurensis; and (4) M. pseudomamillare and M. baghensis. Five oospecies from India have no French equivalents, whereas the oogenus Cairanoolithus is endemic to France. Updated synonymy Megaloolithus oospecies shows a total of nine distinct oospecies from India: Megaloolithus cylindricus, M. mohabeyi, M. padiyalensis, M. jabalpurensis, M. dholiyaensis, M. dhoridungriensis, M. khempurensis, M. megadermus, and M. baghensis. One oospecies, M. jabalpurensis, is common to India and South America and is considered here to be possibly a senior synonym of M. patagonicus. The similarities in egg taxa suggest close phyletic relationships, as well as the probable existence of a terrestrial connection of dinosaur fauna between India and Europe during the Cretaceous, and between the two gondwanan areas Patagonia and India.
Six dinosaurian taxa, Therizinosauridae indet., Ornithomimosauria indet., Dromaeosauridae indet., Titanosauridae indet., cf. Mongolosaurus sp., and Psittacosaurus sp., are identified and described from late Barremian to middle Aptian strata of the Murtoi Formation at the Mogoito locality in Buryatia, western Transbaikalia, Russia. The Mogoito vertebrate assemblage is most similar to the Early Cretaceous assemblages from Khuren Dukh (Mongolia) and Elesitai (Inner Mongolia, China).
Sauropods have a unique digitigrade and semi-tubular manus whose shape has been used as a synapomorphy that unites most sauropod taxa. The vertical orientation and semi-tubular arrangement of the metacarpals suggest the sauropod manus improved the mechanical ability of the forelimb to support great weight. However, the evolutionary mechanism responsible for modifying the relatively flat metacarpus of basal saurischians into a semi-tubular arrangement has remained uninvestigated. Furthermore, trackway evidence shows that manus pronation was more developed in sauropods than other saurischians. However, because the radius and ulna do not cross completely in sauropods, reconciling manus print orientation with forelimb osteology has been difficult. Restudy of North American neosauropod appendicular osteology and anatomy suggests that the unique manus shape of sauropods is linked temporally with reversion to a quadrupedal posture and the necessity of manus pronation. Articulation and manipulation of neosauropod forelimbs and casts, as well as a scale model of Apatosaurus louisae, suggest that, as the sauropod forelimb resumed a weight-bearing role, the primitively anterolateral position of the radius shifted to assume a more internal (anteromedial) orientation in relation to the ulna proximally and distally. The internal shift of the radius may have subsequently pronated the manus while simultaneously altering the shape of the digital arch, transforming a flat dinosaurian manus into a digitigrade, semi-tubular structure. Morphological evidence presented here suggests a semi-tubular manus was an exaptation that ultimately functioned as a weight-distributing structure, and that this unique morphology may have been present in basal sauropods.
Two new species of anhingas are described from upper Miocene–Pliocene (Huayquerian) sediments of southwestern Amazonia, increasing the known diversity of these birds to two genera and at least three, perhaps four, species in these deposits. The new species described here are respectively the largest and the smallest species of Anhingidae known to date. The associated fossil fauna, including gigantic crocodiles and turtles, suggests a flooded paleoenvironment, with large bodies of fresh water surrounded by open vegetation, interspersed by forests.
We present new data on the tooth attachment histology of the Late Cretaceous marine lizard Platecarpus (Mosasauridae). Examination of thin sections of a right dentary reveals the presence of a woven-fiber bone matrix that forms the margins and floor of the tooth alveolus; this bony matrix is traditionally identified as bone of attachment. We identify it as alveolar bone based on its histologic and topologic similarities to archosaurian and mammalian alveolar bone. We also identify a cribiform plate, a structure usually associated with the periodontal ligament. Parallel fibers present in multiple, non-resorbed generations of alveolar bone are tentatively identified as remnants of mineralized portions of collagen fiber bundles, or Sharpey’s fibers. Along the sides of the dentine root we identify a thin layer of acellular cementum. The acellular cementum is surrounded by an enormous mass of cellular cementum tissue that fills the alveolus. This cementum mass is composed of two histologically distinct forms: (1) a loosely organized cellular cementum ground matrix; (2) a laminar form surrounding the vascularization (cementeons) that we term osteocementum. Mosasaurs possess the attachment tissues that are used to diagnose thecodont ankylosis. Mosasaur thecodonty is derived within the Mosasauroidea (aigialosaurs mosasaurs).
A second specimen of the basal therapsid Lemurosaurus pricei preserves aspects of this taxon’s cranial anatomy, such as the structure of the temporal region, palate, and lower jaw, that were either unknown or poorly preserved in the holotype. Although typically considered a dinocephalian feature, intermeshing of the incisors is confirmed for Lemurosaurus. Autapomorphies of the genus include a nubbin-like boss at the apex of the lateral temporal fenestra, the presence of very coarse serrations on the posterior margins of the upper postcanine teeth, and the low, ridge-like form of the median frontal crest.
The anatomical data provided by the new Lemurosaurus specimen permits the first cladistic appraisal of its phylogenetic position among biarmosuchian therapsids. A cladistic analysis of 10 therapsids, two outgroups, and 38 characters indicates that Lemurosaurus is the sister taxon to a clade including Bullacephalus, Proburnetia, and Burnetia. Taxonomically, this position implies the reclassification of Lemurosaurus as a basal burnetiamorph, rather than as an ictidorhinid. Biogeographically, the position of Lemurosaurus makes it most parsimonious to infer that burnetiamorphs originated in southern Africa, although this hypothesis ignores potential sampling biases.
The Kuldana Formation of Pakistan is best known for its fossil mammals, including primitive cetaceans such as Pakicetus and its close relatives. Kuldana mammals have been regarded in different studies as early Lutetian in age (early middle Eocene), late Ypresian (late early Eocene), or, recently, to span much of Ypresian through early Lutetian time (early part of the early Eocene through the early middle Eocene). The Kuldana Formation is a relatively thin, 20–120 m thick low-sea-stand tongue of continental red beds lying within a much thicker sequence of foraminifera-rich marine formations. Planktonic and shallow benthic forams constrain the age of the Kuldana Formation to the late early Eocene or the early middle Eocene, and current interpretation of global sea level stratigraphy favors the latter. The short duration of the low-sea-stand interval when Kuldana mammals are found means that differences between samples recovered to date probably represent differences in local living environments, sites of deposition, and sampling, rather than any substantial difference in age. This reinforces an interpretation first proposed from the perspective of coeval Kalakot mammals recovered from the Subathu Formation in India.
A new species of the diminutive ceratomorph similar to Dilophodon is reported from the latest early Eocene at Desertion Point in the Little Muddy area, Green River Basin, Wyoming. The Little Muddy specimens are assigned to cf. Dilophodon on the basis of their small size, simple premolars, absence of a first lower premolar resulting in a long post-canine diastema, and absence of a hypoconulid on the m3. Cf. Dilophodon destitutus, sp. nov. is the only helaletid known from the latest Early Eocene of the southwestern Green River Basin. It is considerably smaller than other species of Dilophodon. Its premolars are longer and narrower than in Dilophodon leotanus. The lophids on the lower molars are simpler and less posteriorly deflected than in either D. leotanus or Dilophodon minusculus.
Dilophodon was previously known only from the middle Eocene (“Bridger C,” Bridgerian zone Br3) of southwestern Wyoming, and the late Eocene (Uintan, zone Ui3) of Wyoming, northern Utah, Montana, and possibly California. The specimens described here extend the chronologic range of Dilophodon to include the latest early Eocene (lower “Bridger A”; Bridgerian zone Br1b) of the Green River Basin, southwestern Wyoming.
This paper describes new remains of Stegotetrabelodon from Southern Italy, the first evidence of this genus from Eurasia. The material consists of a mandible and a lower tusk fragment collected at Cava Brunia, Cessaniti (Vibo Valentia, Calabria), in late Tortonian Clypeaster-bearing coastal sands. The morphology of the mandible and teeth conforms to the Libyan species S. syrticus, to whom the Italian specimen is referred. The occurrence of this elephantid and other mammal species with african affinity at Cessaniti, suggests that the Calabria-Sicily area was a northern extension of the African continent. The Cessaniti elephantid adds new information on the morphological variability of Stegotetrabelodon and provides clues of an early distribution of the genus since the Tortonian.
Migmacastor procumbodens, gen. et sp. nov. is described from the late Arikareean of Nebraska based on a nearly complete skull. The new taxon exhibits various incisal specializations (e.g., incisors elongated along longitudinal axis, procumbent upper incisors) that are associated with tooth-digging behavior in modern rodents. Migmacastor does not belong in the Palaeocastorinae, the previously recognized fossorial clade of beavers, nor in any other castorid subfamily. Phylogenetic analysis indicates it is more derived than Agnotocastorinae and is a sister taxon to a monophyletic clade of beavers composed of both fossorial and semiaquatic taxa (Castorinae Palaeocastorinae Castoroidinae). Migmacastor is united to the latter unnamed clade by five unambiguous characters: lack of P3; upper tooth rows that diverge posteriorly; P4 larger than molars; smooth enamel on cheek teeth; and longitudinally grooved palate. Preliminary phylogenetic and morphological evidence suggest that tooth-digging behavior arose at least twice in North American beavers.
A very well preserved, incomplete, articulated skeleton with nearly complete skull and mandible of a terrestrial squirrel belonging to the genus Xerus was unearthed at the Pliocene site of Kossom Bougoudi in Chad. Xerus daamsi, sp. nov. is characterized by a narrow nasal associated with medium size. The phylogenetic position of the new species among African Sciuridae was determined using cladistic analysis of craniodental characters. It is most similar to extant Xerus rutilus and Xerus erythropus, currently found in Ethiopia and Chad, respectively. Cladistic analysis also supports the monophyly of the African members of the tribe Xerini, and a sister group relationship between X. daamsi and X. rutilus whose position within the Xerini is poorly supported. The North African genus Atlantoxerus is valid and distinct from Xerus, emphasizing the faunal differences between North African and sub-Saharan regions of the continent. The close affinities of Xerus daamsi with xerines which are currently living in northern savannas, more precisely in the Horn of Africa, suggests the presence of the Somali-Masai vegetation type in Chad by 5 Ma.