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Trilobite cluster from Silurian Rochester Shale.
Full text link16 pages : illustrations (chiefly color) ; 26 cm.Evidence of predator-prey interactions in the fossil record offers important insights into extinct ecosystems. As direct predator-prey relationships are rarely preserved, records of failed predation upon prey species are often considered. The biomineralized exoskeleton of trilobites is exemplary for recording injuries that have resulted from predation. Despite the extensive documentation of trilobite injuries, abnormal specimens are often documented in isolation, with examples of injuries among clustered individuals being poorly known. Here we document a well-preserved body cluster of 18 individuals of the large lichid trilobite Arctinurus boltoni from the mid-Silurian (Wenlock) Rochester Shale of New York, with eight specimens showing injuries. Landmark geometric morphometrics of the specimens is used to explore possible patterns between injured and noninjured specimens. Results of the morphometric analysis indicate that injured and noninjured specimens do not show any systematic difference in overall shape of the exoskeleton, but many of the larger specimens have injuries. The majority of injuries are posteriorly located and right-side dominant, highlighting the possibility of predator or prey lateralization. Biostratinomic evidence suggests that the cluster represents a biological aggregation that was rapidly buried in situ. Potential reasons for this gregarious behavior are discussed, including the possibility that individuals of A. boltoni grouped together to provide "safety in numbers" against predatory attack
Cayman fossil mammals.
Full text link79 pages : illustrations, maps ; 26 cm.Abundant fossils of nesophontid lipotyphlan insectivores and capromyid rodents have been collected from late Quaternary deposits on the Cayman Islands, an island group separated by a major marine barrier from other Caribbean landmasses and isolated from anthropogenic impacts until the arrival of Columbus in 1503 CE. These collections have not previously been formally described. Using morphological and ancient DNA approaches, we document three new taxa of extinct endemic terrestrial mammals from this island group: Nesophontes hemicingulus (Grand Cayman and Cayman Brac), Capromys pilorides lewisi (Grand Cayman, Little Cayman, and Cayman Brac), and Geocapromys caymanensis (Grand Cayman and Cayman Brac). Morphometric comparisons with other extinct and living West Indian mammals indicate that the biogeographic origins of all three new taxa are from source populations on Cuba. Ancient DNA data indicate very low sequence divergence of Capromys pilorides lewisi from mainland Cuban C. pilorides (only 0.5% across the entire mitogenome). Using probabilistic analysis of existing and new radiometric dates, we calculate an estimated extinction date of 1700 CE (95% confidence interval = 1632-1774 CE) for the Cayman Brac Capromys population. This result suggests that at least one endemic Cayman terrestrial mammal population survived for well over a century following first European arrival in the Cayman Islands. The West Indies lost nearly all its species-rich late Quaternary land mammal fauna during the late Holocene due to direct or indirect human impacts, and this study provides a new baseline to understand the magnitude of human-caused mammal extinctions during the recent past
Immature stages of selected meliponine bees (Apoidea, Apidae). (American Museum novitates, no. 3924)
No full text26 pages : illustrations (some color) ; 26 cm.This paper describes the eggs and last larval instars of certain species of bees belonging to the tribe Meliponini, one of the four related tribes that comprise the corbiculate bees in the subfamily Apinae. The four taxa analyzed include some whose immature stages have previously been described. Our purpose is to identify what is known about the anatomy of immature stages and suggest what needs to be studied to better understand the developmental anatomy of eggs and mature larvae in this group of highly eusocial bees
Trans-Saharan Seaway in Mali.
Full text link177 pages, 3 unnumbered leaves of plates (2 folded) : illustrations (chiefly color), maps (some color) ; 26 cm.An epicontinental sea bisected West Africa periodically from the Late Cretaceous to the early Eocene, in dramatic contrast to the current Sahara Desert that dominates the same region today. Known as the Trans-Saharan Seaway, this warm and shallow ocean was a manifestation of globally elevated sea level associated with the rapid break-up of the supercontinent Gondwana in the late Mesozoic. Although it varied in size through time, the Trans-Saharan Seaway is estimated to have covered as much as 3000 km2 of the African continent and was approximately 50 m deep. The edges of the sea were defined in part by the high topography of the Precambrian cratons and mobile belts of West Africa. Over its approximately 50 million year episodic existence, through six major periods of transgression and regression, the Trans-Saharan Seaway left behind extensive nearshore marine sedimentary strata with abundant fossils. The waters that yielded these deposits supported and preserved the remains of numerous vertebrate, invertebrate, plant, and microbial species that are now extinct. These species document a regional picture of ancient tropical life that spanned two major Earth events: the Cretaceous-Paleogene (K-Pg) boundary and the Paleocene-Eocene Thermal Maximum (PETM). Whereas extensive epeiric seas flooded the interior portions of most continents during these intervals, the emerging multicontinental narrative has often overlooked the Trans-Saharan Seaway, in part because fundamental research, including the naming of geological formations and the primary description and analysis of fossil species, remained to be done. We provide such synthesis here based on two decades of fieldwork and analyses of sedimentary deposits in the Republic of Mali. Northern parts of the Republic of Mali today include some of the farthest inland reaches of the ancient sea. We bring together and expand on our prior geological and paleontological publications and provide new information on ancient sedimentary rocks and fossils that document paleoequatorial life of the past. Ours is the first formal description of and nomenclature for the Upper Cretaceous and Lower Paleogene geological formations of this region and we tie these names to regional correlations over multiple modern territorial boundaries. The ancient seaway left intriguing and previously unclassified phosphate deposits that, quite possibly, represent the most extensive vertebrate macrofossil bone beds known from anywhere on Earth. These bone beds, and the paper shales and carbonates associated with them, have preserved a diverse assemblage of fossils, including a variety of new species of invertebrates and vertebrates, rare mammals, and trace fossils. The shallow marine waters included a wide range of paleoenvironments from delta systems, to hypersaline embayments, protected lagoons, and carbonate shoals. Our overarching goal has been to collect vertebrate fossils tied to a K-Pg stratigraphic section in Africa. We provide such a section and, consistent with prior ideas, indicate that there is a gap in sedimentation in Malian rocks in the earliest Paleocene, an unconformity also proposed elsewhere in West Africa. Our phylogenetic analyses of several vertebrate clades across the K-Pg boundary have clarified clade-by-clade species-level survivorship and range extensions for multiple taxa. Few macrofossil species from the Trans-Saharan Seaway show conspicuous change at either the K-Pg boundary or the PETM based on current evidence, although results are very preliminary. Building on our earlier report of the first record of rock-boring bivalves from the Paleocene of West Africa, we further describe here a Cretaceous and Paleogene mollusk fauna dominated by taxa characteristic of the modern tropics. Among the newly discovered fossil osteichthyans, large body size characterizes both the pycnodonts and a new freshwater Eocene catfish species, one of the largest fossil catfishes found in Africa. Our new paleoecological and faunal reconstructions show an evergreen, broadleaf forest that included some of the oldest mangroves known. The ancient Malian ecosystem had numerous apex predators including Crocodyliformes, Serpentes, and Amiidae, some of which were among the largest species in their clades. The Trans-Saharan Seaway exhibited intermittent isolation from major seas. This environmental variable may have created aquatic centers of endemism, stimulating selection for gigantism as previously observed for species on terrestrial islands
New family of myrmecophilic spiders.
Full text link24 pages : illustrations (some color), maps (some color) ; 26 cm.The new genus and species Myrmecicultor chihuahuensis Ramírez, Grismado, and Ubick is described and proposed as the type of the new family, Myrmecicultoridae Ramírez, Grismado, and Ubick. The species is ecribellate, with entelegyne genitalia, two tarsal claws, without claw tufts, and the males have a retrolateral palpal tibial apophysis. Some morphological characters suggest a possible relationship with Zodariidae or Prodidomidae, but the phylogenetic analysis of six markers from the mitochondrial (12S rDNA, 16S rDNA, cytochrome oxidase subunit I) and nuclear (histone H3, 18S rDNA, 28S rDNA) genomes indicate that M. chihuahuensis is a separate lineage emerging near the base of the Dionycha and the Oval Calamistrum clade. The same result is obtained when the molecular data are combined with a dataset of morphological characters. Specimens of M. chihuahuensis were found associated with three species of harvester ants, Pogonomyrmex rugosus, Novomessor albisetosis, and Novomessor cockerelli, and were collected in pitfall traps when the ants are most active. The known distribution spans the Big Bend region of Texas (Presidio, Brewster, and Hudspeth counties), to Coahuila (Cuatro Ciénegas) and Aguascalientes (Tepezalá), Mexico
Dominican Republic fossil land tortoises.
Full text link28 pages : illustrations (chiefly color), map ; 26 cm.A new fossil tortoise, Chelonoidis dominicensis, is described from a flooded cave in La Altagracia Province in the southeastern Dominican Republic on the island of Hispaniola. The holotype, and only known specimen, includes a nearly complete shell, skull, and appendicular skeleton. The new Dominican species, Chelonoidis dominicensis, shares morphological features with the Bahamian tortoise, Chelonoidis alburyorum, and the Cuban tortoise, Chelonoidis cubensis. Chelonoidis dominicensis can be distinguished from C. alburyorum by its weak prognathous-shaped rostrum, stronger and sharper vomerine septum, more angular posterior skull margins, distinctive caudal hump as seen in shell profile, the centrum of first dorsal vertebra narrow without a strong ventral keel, massive sacral buttresses, weak presacral and sacral ribs, more tapered anterior plastral lobe with prominent gulars, elevated gular shelf. An interclavicular sculpture (bird face) occurs on the internal surface of the entoplastron, composed of a massive brow-line and an elongated, narrow keel (beak). Chelonoidis dominicensis is distinguished from C. cubensis (based on incomplete specimens), by its more narrow anterior plastral lobe and gulars, oval entoplastron, a strong wedge-shaped xiphiplastral notch, and a slight ¬indentation at the junction of the cervical sulcus. The West Indian tortoises are allied with Galapagos tortoises, Chelonoidis nigra species complex, and possibly Chaco tortoises, Chelonoidis chilensis, based on morphology. These relationships are further supported by DNA evidence. A second tortoise, Chelonoidis marcanoi, was recently named from dry caves in Pedernales Province, in the southwestern part of the country. The designated holotype for C. marcanoi is a right humerus, but this element is inadequate to differentiate taxa in the West Indian genus Chelonoidis; thus, we consider C. marcanoi a nomen dubium. The concept of multiple populations of tortoises on Hispaniola has merit and is discussed in terms of biotic patterns associated with south and north paleo-islands, which are separated from each other by the Hispaniolan Rift Valley
Sliding joints in diplodocid skulls.
Full text link16 pages : illustrations (chiefly color) ; 26 cm.Diplodocid sauropods had a unique skull morphology, with posteriorly retracted nares, an elongated snout, and anteriorly restricted, peglike teeth. Because of the lack of extant analogs in skull structure and tooth morphology, understanding their feeding strategy and diet has been difficult. Furthermore, the general rarity of sauropod skulls and the fragility of their facial elements resulted in a restricted knowledge of cranial anatomy, in particular regarding the internal surface of the facial skull. Here, we describe in detail a well-preserved diplodocid skull visible in medial view. Diagnostic features recognized in other skulls observable in lateral view, such as the extended contribution of the jugal to the antorbital fenestra, are obliterated in medial view due to extensive overlapping joints between the maxilla, jugal, quadratojugal, and the lacrimal. These overlapping joints permitted limited anterior sliding movement of the snout, which likely served as a kind of "shock-absorbing" mechanism during feeding. Diplodocid skulls therefore seem to have evolved to alleviate stresses inflicted on the snout during backward movements of the head, as would be expected during branch-stripping or raking
Revision Balsateres, Kuarapu, and Thorellius.
Full text link81 pages : illustrations (some color), maps ; 26 cm.Four genera formed a monophyletic group, referred to as the Kochius clade, in the phylogeny of the North American vaejovid scorpion subfamily Syntropinae Kraepelin, 1905: Balsateres González-Santillán and Prendini, 2013; Kochius Soleglad and Fet, 2008; Kuarapu Francke and Ponce-Saavedra, 2010; and Thorellius Soleglad and Fet, 2008. In the present contribution, all except Kochius, treated elsewhere, are revised. The monotypic Balsateres and Kuarapu are redescribed. Thorellius cristimanus (Pocock, 1898) and Thorellius intrepidus (Thorell, 1876) are redescribed and their type localities discussed and clarified. Three new species of Thorellius are described: Thorellius tekuani; Thorellius wixarika; and Thorellius yuyuawi. Vaejovis intrepidus atrox Hoffmann, 1931, is newly synonymized with T. cristimanus based on examination of the type material. A key to identification of the species of Thorellius is presented, and new locality records and updated distribution maps provided for all species covered
Bombus impatiens, Including observations on its egg eclosion.
Full text link25 pages : illustrations (some color) ; 26 cm.This contribution results from an investigation of four commercially obtained colonies of Bombus (Pyrobombus) impatiens Cresson in an attempt to understand the functional anatomy and behavior of its immature stages. Eggs are described in detail, and their chorionic microstructure is contrasted with that of Bombus (Cullumanobombus) griseocollis (De Geer). They are deposited in groups consisting of a few to more than nine eggs into a single chamber. The study confirms that larvae pass through four instars. Although increasing in size dramatically from one instar to the next, larval anatomy and behavior change little during the first three instars. The last instar is the one that commences defecation and production of silk resulting in cocoon construction. In contrast to most bees, its larval activities result in substantial changes in size and shape of its brood chamber, whereas brood chambers of most bees are constructed by the female and modified little by the offspring. This study is a part of a series of investigations into the similarities and differences in the developmental biologies among corbiculate bees
P. quica, P. canus, and a new species from Amazonia.
Full text link70 pages : illustrations (some color), maps (some color) ; 26 cm. "Appendix 5. On the type locality of Didelphys frenata Olfers, 1818 / Robert S. Voss and Renate Angermann": pages 69-70.This is the first installment of a revision of the didelphid marsupial genus Philander, commonly known as gray four-eyed opossums. Although abundant and widespread in lowland tropical forests from southern Mexico to northern Argentina, species of Philander are not well understood taxonomically, and the current literature includes many examples of conflicting species definitions and nomenclatural usage. Our revision is based on coalescent analyses of mitochondrial gene sequences, phylogenetic analyses of mitochondrial and nuclear genes, morphometric analyses, and firsthand examination of relevant type material. Based on these results, we provisionally recognize eight species, of which three are formally treated in this report: P. quica (Temminck, 1824), an Atlantic Forest endemic formerly known as P. frenatus (Olfers, 1818); P. canus (Osgood, 1913), a widespread species formerly treated as a synonym or subspecies of P. opossum (Linnaeus, 1758); and P. pebas, a new species endemic to Amazonia. The remaining, possibly valid, species of Philander can be allocated to two clades. The first is a cis-Andean complex that includes P. andersoni (Osgood, 1913); P. mcilhennyi Gardner and Patton, 1972; and P. opossum. The second is a trans-Andean complex that includes P. melanurus (Thomas, 1899) and P. pallidus (Allen, 1901). Among other nomenclatural acts, we designate a neotype for the long-problematic nominal taxon Didelphis superciliaris Olfers, 1818, and (in an appendix coauthored by Renate Angermann), we establish that Olfers' coeval binomen D. frenata is based on an eastern Amazonian type and is a junior synonym of P. opossum