Bones of recent mammals in the Amboseli Basin, southern Kenya, exhibit distinctive weathering characteristics that can be related to the time since death and to the local conditions of temperature, humidity and soil chemistry. A categorization of weathering characteristics into six stages, recognizable on descriptive criteria, provides a basis for investigation of weathering rates and processes. The time necessary to achieve each successive weathering stage has been calibrated using known-age carcasses. Most bones decompose beyond recognition in 10 to 15 yr. Bones of animals under 100 kg and juveniles appear to weather more rapidly than bones of large animals or adults. Small-scale rather than widespread environmental factors seem to have greatest influence on weathering characteristics and rates. Bone weathering is potentially valuable as evidence for the period of time represented in recent or fossil bone assemblages, in- cluding those on archeological sites, and may also be an important tool in censusing populations of animals in modern ecosystems.

Taphonomic and Ecologic Information Form Bone Weathering

The vertebrate fauna of the Cloverly Formation has been studied for more than 75 years, but remains poorly sampled and incompletely understood. We undertook an extensive survey of the formation that resulted in the discovery of several new, highly productive vertebrate microfossil bonebeds (VMBs). Comprehensive sampling of these and other sites has nearly doubled the known vertebrate diversity of the Cloverly Formation. In addition to the comparatively well-known dinosaurs, this augmented faunal list includes hybodontoid sharks, numerous bony fishes, three lissamphibian lineages, lizards, multiple crocodylians, and several new mammal occurrences. The known Cloverly vertebrate fauna now more closely resembles those of other late Early Cretaceous formations in North America, indicating broad similarities across wide geographic areas at this time. In addition, this work underscores the important role VMBs can play in areas previously studied primarily through surface prospecting and quarrying, espec...

https://bioone.org/journals/Journal-of-Vertebrate-Paleontology/volume-33/issue-2/02724634.2012.717567/Vertebrate-Paleontology-of-the-Cloverly-Formation-Lower-Cretaceous-I/10.1080/02724634.2012.717567.pdf

Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), I: faunal composition, biogeographic relationships, and sampling

Despite long-standing significance in the annals of North American stratigraphy and paleontology, key aspects of the Upper Cretaceous Judith River Formation remain poorly understood. We re-evaluate Judith River stratigraphy and propose new reference sections that both document the range of lithologies present in the type area in north-central Montana and reveal dramatic changes in facies architecture, fossil content, and rock accumulation rates that can be mapped throughout the type area and into the plains of southern Alberta and Saskatchewan. One section spans the basal contact of the Judith River Formation with marine shales of the underlying Claggett Formation. This contact, which lies along the base of the Parkman Sandstone Member of the Judith River Formation, is erosional and consistent with an episode of forced regression, contrary to previous descriptions. A second reference section spans the entire Judith River Formation. This complete section hosts a lithologic discontinuity, herein ref...

Age, Correlation, and Lithostratigraphic Revision of the Upper Cretaceous (Campanian) Judith River Formation in Its Type Area (North-Central Montana), with a Comparison of Low- and High-Accommodation Alluvial Records

The Mesozoic and Palaeocene record of lissamphibians (i.e. anurans, caudates, gymnophionans and albanerpetontids) in North America is reviewed on the basis of over 400 published and unpublished occurrences from 61 geological formations. The record is heavily biased towards isolated bones, although some associated and articulated skeletons and rare tracks and trackways are known. Most of the localities are in the Western Interior: in central and southern Alberta and southern Saskatchewan, Canada, extending southwards through the USA and into northern Mexico. Outside of that region, records are limited to one Late Cretaceous age formation in Baja California and several Late Triassic and Cretaceous age formations in the eastern USA. Putative lissamphibians have been reported from the Late Triassic (middle Carnian and early Norian). Unambiguous lissamphibians are known from the Early Jurassic (Sinemurian–Pliensbachian), the Late Jurassic (Kimmeridgian–earliest Tithonian), the basal Cretaceous (late Berriasian–Valanginian) and a nearly continuous sequence extending from the Aptian through to the terminal Palaeocene. The Early Jurassic (Sinemurian–Pliensbachian) of Arizona documents the oldest global occurrences of an anuran (i.e. crown frog) and a stem caecilian; the latter also is the only North American fossil occurrence for Gymnophiona prior to the Quaternary. Late Jurassic (Kimmeridgian–earliest Tithonian) age deposits in Colorado, Utah and Wyoming contain a moderate diversity of anurans, urodeles (i.e. crown salamanders) and possibly stem salamanders. A basal Cretaceous locality (late Berriasian–Valanginian) in South Dakota contains a urodele and the first North American occurrence for Albanerpetontidae. Aptian/Albian age localities in Montana, Wyoming, Texas and Oklahoma contain a mixture of anurans, urodeles and albanerpetontids—that tripartite lissamphibian composition persists in North America through the remainder of the Cretaceous and intermittently through the Palaeocene. Most of the anurans are of uncertain familial affinities. The urodeles contain a mixture of extinct families (Scapherpetontidae and Batrachosauroididae) that were prominent through the Cretaceous into the early Palaeogene, along with the earliest appearances of several extant families, specifically sirenids in the Santonian, amphiumids and proteids in the late Maastrichtian and dicamptodontids and unequivocal cryptobranchids in the late Palaeocene. The albanerpetontid genus Albanerpeton was moderately diverse during the Cretaceous and Palaeocene, before vanishing from the North American record near the end of the Palaeocene. Temporal richness estimates of North American lissamphibians were calculated based on taxic and minimum lineage level occurrence data per 5 million year time interval beginning in the Early Jurassic and though to the end of the Palaeocene. The resulting richness curves demonstrate a general pattern of increasing richness leading up to the Cretaceous-Palaeogene (K-Pg) boundary, with peak values during the Campanian and Maastrichtian and a decline thereafter. The latter part of that pattern suggests higher extinction rates for lissamphibians across the K-Pg boundary compared to previous estimates, which we attribute to our coarser temporal binning, taxonomic additions and changes to some earlier taxonomic identifications. Although the overall richness pattern may at least partially reflect a true signal, it is heavily influenced by factors such as taphonomy, temporal gaps, fossil sampling and publication biases towards particular intervals and taxonomic groups; more detailed studies of all major lissamphibian clades are needed to corroborate these findings. This review highlights the strengths and weaknesses of the Mesozoic and Palaeocene portion of the North American lissamphibian record and provides a framework for future work.

Mesozoic and Palaeocene lissamphibian assemblages of North America: a comprehensive review

This study reports on a new ceratopsid, Spiclypeus shipporum gen et sp. nov., from the lower Coal Ridge Member of the Judith River Formation in Montana, USA, which dates to ~76 Ma (upper Campanian). The species is distinguished by rugose dorsal contacts on the premaxillae for the nasals, laterally projecting postorbital horncores, fully fused and anteriorly curled P1 and P2 epiparietals, and a posterodorsally projecting P3 epiparietal. The holotype specimen is also notable for its pathological left squamosal and humerus, which show varied signs of osteomyelitis and osteoarthritis. Although the postorbital horncores of Spiclypeus closely resemble those of the contemporaneous ‘Ceratops’, the horncores of both genera are nevertheless indistinguishable from those of some other horned dinosaurs, including Albertaceratops and Kosmoceratops; ‘Ceratops’ is therefore maintained as a nomen dubium. Cladistic analysis recovers Spiclypeus as the sister taxon to the clade Vagaceratops + Kosmoceratops, and appears transitional in the morphology of its epiparietals. The discovery of Spiclypeus adds to the poorly known dinosaur fauna of the Judith River Formation, and suggests faunal turnover within the formation.

/pdf/spiclypeus-shipporum-gen-et-sp-nov-a-boldly-audacious-new-5buir4uuhm.pdf

Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA

Microfossil bonebeds are multi-individual accumulations of disarticulated and dissociated vertebrate hardparts dominated by elements in the millimeter to centimeter size range (≥75% of bioclasts ≤5 cm maximum dimension). Modes of accumulation are often difficult to decipher from reports in the literature, although predatory (scatological) and fluvial/hydraulic origins are typically proposed. We studied the sedimentology and taphonomy of 27 microfossil bonebeds in the Campanian Judith River Formation of Montana in order to reconstruct formative histories. Sixteen of the bonebeds examined are hosted by fine-grained facies that accumulated in low-energy aquatic settings (pond/lake microfossil bonebeds). Eleven of the bonebeds are embedded in sandstones that accumulated in ancient fluvial settings (channel-hosted microfossil bonebeds). In lieu of invoking separate pathways to accumulation based on facies distinctions, we present a model that links the accumulation of bioclasts in the two facies. We p...

https://bioone.org/journals/paleobiology/volume-36/issue-1/0094-8373-36.1.80/Origins-of-microfossil-bonebeds--insights-from-the-Upper-Cretaceous/10.1666/0094-8373-36.1.80.pdf

Origins of microfossil bonebeds: insights from the Upper Cretaceous Judith River Formation of north-central Montana

Regional comprehensive universities with access-oriented missions provide critical pathways for increasing the number and diversity of STEM graduates. The BOND program at California State University, Fresno supports the transition to college for first-time, full-time freshmen in selected STEM majors. BOND incorporates a learning community, active learning, and early course-based research experiences. Compared to comparison groups, students that participate in BOND are 1.93 times more likely to persist in STEM into their fourth year despite similar academic achievement in introductory STEM courses. A higher proportion of BOND students also engage with campus resources that support their first and second year on campus, which suggests that appropriate support builds persistence through the challenges of a STEM degree. This study highlights the importance of providing support strategies and resources in the first year for STEM retention, counter to the traditional narrative of “weeding out” students in their first year on campus.

Cultivating not Weeding: STEM First Year Learning Community Fosters Student Persistence and Engagement

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Origins of microfossil bonebeds: insights from the Upper Cretaceous Judith River Formation of north-central Montana

Cultivating not Weeding: STEM First Year Learning Community Fosters Student Persistence and Engagement