Jonathan Ivan Bloch

• Ph.D. University of Michigan
• Curator at University of Florida

The Microsyopidae are extinct mammals from the late Paleocene–late Eocene of North America and the late Paleocene of Europe. While results from phylogenetic analyses support euarchontan affinities, specific relationships of microsyopids to other plesiadapiforms (plausible stem primates), Euprimates (crown primates), Scandentia (treeshrews), and Der...

Mammalian molar crowns form a module in which measurements of size for individual teeth within a toothrow covary with one another. Molar crown size covariation is proposed to fit the inhibitory cascade model (ICM) or its variant the molar module cascade model (MMC), but the inability of the former model to fit across biological scales is a concern...

Interpreting the impact of climate change on vertebrates in the fossil record can be complicated by the effects of potential biotic drivers on morphological patterns observed in taxa. One promising area where this impact can be assessed is a high-resolution terrestrial record from the Bighorn Basin, Wyoming, that corresponds to the Paleocene–Eocene...

The Mesonychia is a group of archaic carnivorous mammals of uncertain phylogenetic affinities with a Holarctic distribution during the Paleogene. Intensive fossil collecting efforts in the Bighorn Basin, Wyoming, have resulted in recovery of the largest sample and most complete specimens yet known of the mesonychid Dissacus praenuntius from the sec...

The absence of terrestrial apex predators on oceanic islands led to the evolution of endemic secondary apex predators like birds, snakes and crocodiles, and loss of defence mechanisms among species. These patterns are well documented in modern and Quaternary terrestrial communities of the West Indies, suggesting that biodiversity there assembled si...

Marine sedimentary rocks of the late Eocene Pagat Member of the Tanjung Formation in the Asem Asem Basin near Satui, Kalimantan, provide an important geological archive for understanding the paleontological evolution of southern Kalimantan (Indonesian Borneo) in the interval leading up the development of the Central Indo-Pacific marine biodiversity...

Analyses of rock samples collected during recent fieldwork in the Ombilin Basin of west-central Sumatra, Indonesia yielded pollen data that constrain the age and depositional setting of associated plant macrofossil and vertebrate fossil-bearing units in the Sangkarewang and Sawahlunto formations. Articulated fish and plant fossils were recovered fr...

Mixodectids are poorly understood placental mammals from the Paleocene of western North America that have variably been considered close relatives of euarchontan mammals (primates, dermopterans, and scandentians) with hypothesized relationships to colugos, extinct plagiomenids, and/or microsyopid plesiadapiforms. Here we describe the most complete...

Nine years of excavations at Montbrook (ca. 5.9 Ma, Levy Co., Florida) have recovered ca. 250,000 vertebrate fossils from an area of 525 m 2. Over 90% are fish, alligator, turtle, and other aquatic taxa; this in addition to sedimentological evidence supports a fluvial depositional environment. Three fossil-bearing units are recognized, Strata 2, 2A...

Premise of research. The Neogene collision of the Australian tectonic plate (Sahul) with Southeast Asia (Sunda) restructured the vegetation of both regions. The rarity of plant macrofossils from Sunda has limited the understanding of precollision vegetation and plants that migrated from Sunda to Sahul. Despite the importance of legumes in the livin...

Analysis of largely unstudied fossil collections recovered from caves and sinkholes from western Hispaniola has resulted in the recognition of a new capromyine rodent (Zagoutomys woodsi, gen. et sp. nov.) and a new solenodontid (Solenodon ottenwalderi sp. nov.). Fossils of Z. woodsi show that it differs from other capromyine rodents in having a man...

The 2015–2023 excavations at the Montbrook Site in Levy County, north-central Florida, recovered more than 125,000 vertebrate fossils from an area of about 500 m2 . Of these, over 90% are from aquatic or semi-aquatic taxa. The site’s age is latest Miocene (late Hemphillian), ca. 5.5–5.8 Ma, based on mammalian biochronology. The depositional environ...

New World porcupines (Erethizontinae) originated in South America and dispersed into North America as part of the Great American Biotic Interchange (GABI) 3-4 million years ago. Extant prehensile-tailed porcupines (Coendou) today live in tropical forests of Central and South America. In contrast, North American porcupines (Erethizon dorsatum) are t...

Moderately diverse trace fossil assemblages occur in the Eocene Tambak Member of the Tanjung Formation, in the Asem Asem Basin on the southern coast of South Kalimantan. These assemblages are fundamental for establishing depositional models and paleoecological reconstructions for southern Kalimantan during the Eocene and contribute substantially to...

Fossils of an insectivorous bat from the early Miocene of Panama are described as a new genus and species, Americanycteris cyrtodon (Chiroptera: Phyllostomidae: Phyllostominae). Americanycteris is a large phyllostomine bat, similar in size to the living species Chrotopterus auritus. Americanycteris cyrtodon can be distinguished from other closely r...

Establishment of extant terrestrial vertebrate faunas in North America was influenced by a set of factors associated with temporal changes in climate and ecology that operated at different geographic scales. While the biogeography of extant taxa can be inferred from phylogenies, these omit lineages that have gone regionally extinct and for which th...

With a few exceptions, crown-clade Primates differ from other arboreal mammalian clades by having nails instead of claws on most post-axial digits. Distal phalanx morphology of close extant and fossil relatives of crown-clade Primates provides a context in which to study the evolution of this characteristic feature. Plesiadapiforms are a diverse gr...

Hispaniola (Haiti & Dominican Republic (D.R.)), is the second largest island in the Caribbean and is a hotspot of squamate diversity (~184 species), yet little is known about their fossil record and how it relates to the present. Past studies on mammalian communities suggest that many rodent species go extinct after human arrival (~7,000 y.B.P.), m...

Abilities of taxa to track suitable habitat under climate change is a concern in conservation biology. Projections that assume suitable habitat is limited to currently occupied biomes can produce underestimates of species viability. The geological record is a valuable source of data to test assumptions about habitat tracking because it archives pas...

Paleogene microsyopid plesiadapiforms are among the oldest euarchontans known from relatively complete crania. While cranial endocasts are known for larger-bodied Eocene microsyopine micro-syopids, this study documents the first virtual endocast for the more diminutive uintasoricine micro-syopids, derived from a specimen of Niptomomys cf. Niptomomy...

The Paleogene epoch was a dynamic time for mammalian evolution, including the fossil relatives of primates. Several adaptively significant features of the primate foot first appear in fossils from the Paleogene, and relatives of most extant primate groups are recognizable in the fossil record by the end of the Oligocene. This chapter reviews the mo...

Hispaniola is the second-largest island in the West Indies bioregion and along with Cuba is considered the cradle of Greater Antillean rodent evolution and diversification. While the fossil record in Hispaniola includes ten extinct species of late Quaternary rodents, only a single species, the Hispaniola hutia (Plagiodontia aedium), is extant on th...

In neutral models of quantitative trait evolution, both genetic and phenotypic divergence scale as random walks, producing a correlation between the two measures. However, complexity in the genotype‐phenotype map may alter the correlation between genotypic and phenotypic divergence, even when both are evolving neutrally or nearly so. Understanding...

Division of the dentition into morphologically distinct classes of teeth (incisors, canines, premolars, and molars) and the acquisition of tribosphenic molars facilitated precise occlusion between the teeth early in mammal evolution. Despite the evolutionary and ecological importance of distinct classes of teeth with unique cusp, crest, and basin m...

We describe a new diminutive early Eocene lizard, Blutwurstia oliviae, gen. et sp. nov., on the basis of associated cranial and postcranial remains from the Clarks Fork Basin of Wyoming. Results from phylogenetic analyses suggest that B. oliviae is on the stem of knob-scaled lizards (Xenosaurus), a relict extant clade of specialized, stenotopic cre...

Sloths were among the most diverse groups of land vertebrates that inhabited the Greater Antilles until their extinction in the middle-late Holocene following the arrival of humans to the islands. Although the fossil record of the group is well known from Quaternary deposits in Cuba, Hispaniola, and Puerto Rico, remains from older units are scarce,...

The living tree sloths Choloepus and Bradypus are the only remaining members of Folivora, a major xenarthran radiation that occupied a wide range of habitats in many parts of the western hemisphere during the Cenozoic, including both continents and the West Indies. Ancient DNA evidence has played only a minor role in folivoran systematics, as most...

Omomyiform primates are among the most basal fossil haplorhines, with the oldest classified in the genus Teilhardina and known contemporaneously from Asia, Europe, and North America during the Paleocene-Eocene Thermal Maximum (PETM) ~56 mya. Characterization of morphology in this genus has been limited by small sample sizes and fragmentary fossils....

The Paleocene-Eocene Thermal Maximum (PETM) is a brief interval of rapid global warming (~5-10° C) that occurred ~56 mya. The mammal fossil record across the PETM documents decreases in body size among ~40% of lineages, including two microsyopid plesiadapiforms (stem primates):--the uintasoricine Niptomomys and microsyopine Arctodontomys--with a su...

Euprimates are unusual among mammals in having fingers and toes with flat nails. While it seems clear that the ancestral stock from which euprimates evolved had claw-bearing digits, the available fossil record has not yet contributed a detailed understanding of the transition from claws to nails. This study helps clarify the evolutionary history of...

The Paleocene-Eocene Thermal Maximum (PETM) was a period of transient global warming, when temperature increased rapidly by ~5-8° C, was sustained for ~100 kyrs, then gradually returned to background. The PETM altered terrestrial ecology through changes in aridity, seasonality, and floral community composition. Among mammals, the PETM is associated...

Accurate, quantitative characterization of complex shapes is recognized as a key methodological challenge in biology. Recent development of automated three-dimensional geometric morphometric protocols (auto3dgm) provides a promising set of tools to help address this challenge. While auto3dgm has been shown to be useful in characterizing variation a...

Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptiv...

Electronic Supplementary Material: Oldest skeleton of a plesiadapiform provides evidence for an exclusively arboreal radiation of stem primates in the Paleocene

The Florida Mouse Podomys floridanus and the Gopher Tortoise Gopherus polyphemus are linked in modern ecosystems by a commensal relationship in which Podomys uses the burrows of Gopherus. However, previous paleoecological research demonstrated that species interactions, including commensalisms, are not necessarily stable through geologic time. Give...

The earliest fossil euprimates appear in strata corresponding to an intense, brief episode of global warming, when temperature increased by >5° C in less than 20 kyr and remained elevated for ~120 kyr before returning to background levels. Known as the Paleocene-Eocene Thermal Maximum (PETM), this event significantly altered North American floral c...

Very shortly after the disappearance of the non-avian dinosaurs, the first mammals that had features similar to those of primates started appearing. These first primitive forms went on to spawn a rich diversity of plesiadapiforms, often referred to as archaic primates. Like many living primates, plesiadapiforms were small arboreal animals that gene...

The oldest fossil euprimates from North America include adapoids (Cantius) and omomyoids (Teilhardina) that appear during a major global warming event known as the Paleocene-Eocene Thermal Maximum (PETM) ~56 mya. Teilhardina had a Holarctic distribution during the earliest Eocene, represented in North America by T. brandti, T. gingerichi, and T. ma...

Sexual dimorphism and intrasexual competition between males is hypothesized to have appeared early in primate evolution, based on inferred canine dimorphism in the most basal adapiform, Cantius torresi and its later occurring notharctine relatives. Previous studies assessing canine dimorphism in notharctines have only made comparisons with a limite...

Body mass prediction is a frequent goal of paleontologists since body mass covaries with many aspects of a species' ecology. For example, niche partitioning by body mass (as predicted from tooth size) is often invoked in mammalian paleocommunities. However, tooth size can vary independent of body mass, and this variation has important ecological im...

Quantifying the relationship between carbon cycle perturbations and the hydrologic cycle in the geologic past is crucial to accurately modeling how future anthropogenic carbon emissions and resulting radiative forcing might affect the hydrologic cycle. Interpreting changes in proxy records for insight into paleohydrologic change is complex, and doc...

To understand the hand of living primates from an adaptive perspective, data on the morphological pattern of the earliest primates is required. This chapter discusses what is known about the early evolution of primate hands based on fossils of Paleogene plesiadapiforms (potential stemprimates), adapiforms, omomyiforms, and anthropoids. Implications...

Primate species typically differ from other mammals in having bony canals that enclose the branches of the internal carotid artery (ICA) as they pass through the middle ear. The presence and relative size of these canals varies among major primate clades. As a result, differences in the anatomy of the canals for the promontorial and stapedial branc...

Well-preserved crania of notharctine adapiforms from the Eocene of North America provide the best direct evidence available for inferring neuroanatomy and encephalization in early euprimates (crown primates). Virtual endocasts of the notharctines Notharctus tenebrosus (n = 3) and Smilodectes gracilis (n = 4) from the middle Eocene Bridger formation...

Paleogene micromomyids are small (∼10–40 g) euarchontan mammals with primate-like molars and postcrania suggestive of committed claw-climbing positional behaviors, similar to those of the extant arboreal treeshrew, Ptilocercus. Based primarily on evidence derived from dental and postcranial morphology, micromomyids have alternately been allied with...

New World monkeys (platyrrhines) are a diverse part of modern tropical ecosystems in North and South America, yet their early evolutionary history in the tropics is largely unknown. Molecular divergence estimates suggest that primates arrived in tropical Central America, the southern-most extent of the North American landmass, with several dispersa...

The Paleocene-Eocene thermal maximum was a period of abrupt, transient global warming, fueled by a large release of ¹³Cdepleted carbon and marked globally by a negative carbon isotope excursion. While the carbon isotope excursion is often identified in the carbon isotope ratios of bulk soil organic matter (δ¹³Corg), these records can be biased by f...

There are five major scenarios that have been advanced to account for the early events in the origination of the order Primates: a transition from terrestriality to arboreality, the adoption of a grasp-leaping mode of locomotion, the evolution of features for visual predation, an adaptation to terminal branch feeding occurring during angiosperm div...

The cephalic shield of cingulates is a structure comprised of sutured osteoderms that is highly variable in overall shape and number of osteoderms across different taxa. The cephalic shields of the extinct giant armadillos (pampatheres) are poorly known. The late Blancan Haile 7G locality in north-central Florida has produced the largest known asse...

Although variation in cranial arterial presence, route and development has been shown to provide indications of phylogenetic relationship in primates, information on relative area of the promontorial and stapedial bony canals has never been comprehensively quantified. Among fossil euprimates, some genera (notably Mahgarita, Notharctus, and Rooneyia...

Although Cenozoic protoceratid artiodactyls are known from throughout North America, species referred to the Miocene protoceratine Paratoceras are restricted to subtropical areas of the Gulf Coast and southern Mexico and tropical areas of Panama. Newly discovered fossils from the late Arikareean Lirio Norte Local Fauna, Panama Canal basin, include...

Gomphochelys nanus, new genus and species, is described from the earliest Wasatchian (biohorizon Wa 0; ∼55.8 Ma) of the southeastern Bighorn Basin, Washakie County, Wyoming. The new taxon represents the only known dermatemydid from the Paleocene-Eocene Thermal Maximum (PETM) interval and extends the lineage back from previous records by approximate...