Papers by Stephanie A Maiolino
The 86th Annual Meeting of the American Association of Physical Anthropologists, New Orleans, 2017
Journal of Mammalian Evolution
Journal of human evolution, 2018
Euprimates are unusual among mammals in having fingers and toes with flat nails. While it seems c... more 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 second pedal digit with fossils representing the distal phalanx of digit two (dpII), and has broader implications for other digits. Among extant primates, the keratinized structure on the pedal dpII widely varies in form. Extant strepsirrhines and tarsiers have narrow, distally tapering, dorsally inclined nails (termed a 'grooming claws' for their use in autogrooming), while extant anthropoids have more typical nails that are wider and lack distal tapering or dorsal inclination. At least two fossil primate species thought to be stem members of the Strepsirrhini appear to have had grooming claws, yet reconstructions of the ance...
Developments in Primatology: Progress and Prospects, 2016
The primate hand consists of five rays: a pollex containing a metacarpal and two phalanges and fo... more The primate hand consists of five rays: a pollex containing a metacarpal and two phalanges and four ulnar rays each containing a metacarpal and three phalanges. Morphology of these elements is related to a number of factors including behavior (such as locomotor mode and manipulatory capabilities) and phylogenetic relatedness. This chapter briefly reviews the evolutionary history of the primate hand, discusses the intrinsic proportions of bones within the rays, and emphasizes the general osteology and morphological diversity among primates and their close relatives. The functional and evolutionary consequences of anatomical specializations are reviewed. Where clear gaps in the literature exist, new preliminary descriptions and data are presented.
Developments in Primatology: Progress and Prospects, 2016
The integument of primate hands (i.e., skin and nails) are specialized to interact with the outsi... more The integument of primate hands (i.e., skin and nails) are specialized to interact with the outside world. The integument of the palm is arranged into a series of fleshy volar pads, while hardened nails grow from the skin overlying the tips of the digits. The volar skin provides friction which enhances climbing ability and the prehension of objects, but also contains important mechanoreceptors for tactile acuity. Primate nails are highly diverse in structure and likely play a number of different roles related to locomotion, grasping, and tactile sensitivity. This chapter provides a comprehensive review of the integument of primate hands. First, the structure of volar skin and nails is discussed. This is followed by a review of the anatomical diversity among nonhuman primates and a discussion of the functional significance of different specializations. The chapter ends with avenues for future study.
PLoS ONE, 2012
Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of livi... more Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of living anthropoids (monkeys, apes, and humans). Central to this argument is the form of the second pedal digit. Extant strepsirrhines and tarsiers possess a grooming claw on this digit, while most anthropoids have a nail. While controversial, the possible presence of a nail in certain European adapiforms has been considered evidence for anthropoid affinities. Skeletons preserved well enough to test this idea have been lacking for North American adapiforms. Here, we document and quantitatively analyze, for the first time, a dentally associated skeleton of Notharctus tenebrosus from the early Eocene of Wyoming that preserves the complete bones of digit II in semi-articulation. Utilizing twelve shape variables, we compare the distal phalanges of Notharctus tenebrosus to those of extant primates that bear nails (n = 21), tegulae (n = 4), and grooming claws (n = 10), and those of non-primates that bear claws (n = 7). Quantitative analyses demonstrate that Notharctus tenebrosus possessed a grooming claw with a surprisingly well-developed apical tuft on its second pedal digit. The presence of a wide apical tuft on the pedal digit II of Notharctus tenebrosus may reflect intermediate morphology between a typical grooming claw and a nail, which is consistent with the recent hypothesis that loss of a grooming claw occurred in a clade containing adapiforms (e.g. Darwinius masillae) and anthropoids. However, a cladistic analysis including newly documented morphologies and thorough representation of characters acknowledged to have states constituting strepsirrhine, haplorhine, and anthropoid synapomorphies groups Notharctus tenebrosus and Darwinius masillae with extant strepsirrhines rather than haplorhines suggesting that the form of pedal digit II reflects substantial homoplasy during the course of early primate evolution.
The Anatomical Record, 2011
Grooming claws are present on the second pedal digits of strepsirhines and on the second and thir... more Grooming claws are present on the second pedal digits of strepsirhines and on the second and third pedal digits of tarsiers. However, their presence in New World monkeys is often overlooked. As such, the absence of a grooming claw is generally considered an anthropoid synapomorphy. This study utilizes a quantitative multivariate analysis to define grooming claw morphology and document its presence in platyrrhine monkeys. Our results show that owl monkeys possess grooming claws similar to those of strepsirhines, while titi monkeys possess grooming claw‐like morphology. Therefore, we conclude that anthropoids are not clearly united by the absence of a grooming claw. Furthermore, due to their presence in three major primate clades, we infer that it is likely that a grooming claw was present on the second pedal digit of the ancestor of living primates. Therefore, we advise the reassessment of fossil adapids in light of the anatomical correlates described here. This should increase resol...
2017 Maiolino SA. Middle phalanx morphology reflects postural differences of primate grooming and... more 2017 Maiolino SA. Middle phalanx morphology reflects postural differences of primate grooming and nail-bearing digits. American Journal of Physical Anthropology, 162(S64):273 2017 Boyer DM, Maiolino SA, Holroyd PA, Morse PE, Bloch JI. Evidence for grooming claws in the earliest omomyids. American Journal of Physical Anthropology, 162(S64):127-128 2016 Maiolino SA. Anthropoid grooming ungues and ancestral state estimations of second pedal unguis form. American Journal of Physical Anthropology, 159(S62):217. 2015 Maiolino SA, Huang S, Boyer DM. Nail-like distal phalanges on postaxial digits are related to the use of a terminal branch niche in non-primate mammals. American Journal of Physical Anthropology, 156(S60):211. 2014 Maiolino SA. Identifying homologies among claws and nails: Implications for primate evolution. American Journal of Physical Anthropology, 153(S58):175. 2013 Maiolino SA, Boyer DM. Distal phalangeal evolution in early euprimates. Journal of Vertebrate Paleontology, ...
The primate forelimb consists of three segments distal to the pectoral girdle. The most proximal ... more The primate forelimb consists of three segments distal to the pectoral girdle. The most proximal is the brachium (the arm), which contains the single humerus. The middle segment is the antebrachium (the forearm), which contains two bones, the radius and ulna. The distal segment is the manus (hand), which contains several bones within the carpus (wrist), the metacarpus (palm), and the digits (fi ngers). Collectively, the metacarpus and digits form the digital rays of the hand. The hand, including the carpus, can account for 20-42 % of total forelimb length across primates .1 ). The rays are numbered 1-5 from radial to ulnar. The fi rst ray is the thumb (pollex), and this is followed by the index (demonstratorius or pointer), middle (medius), ring (annularis), and little (minimus) fi ngers according to the conventional terminology used for the human hand. Historically, each digit has been referred to by various names, but typical among nonhuman primates the thumb is referred to as the pollex and the remaining rays as ulnar rays 2 through 5. The interested reader is encouraged to see Napier ( 1980 ) for a more colorful and detailed history of hand ray nomenclature. The focus of this chapter is on the digital rays of the hand.
Palaeobiodiversity and Palaeoenvironments, 2015
Your article is protected by copyright and all rights are held exclusively by Senckenberg Gesells... more Your article is protected by copyright and all rights are held exclusively by Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Evolutionary Anthropology: Issues, News, and Reviews, 2013
Evolutionary Anthropology: Issues, News, and Reviews, 2011
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Anatomical Record, 2011
Grooming claws are present on the second pedal digits of strepsirhines and on the second and thir... more Grooming claws are present on the second pedal digits of strepsirhines and on the second and third pedal digits of tarsiers. However, their presence in New World monkeys is often overlooked. As such, the absence of a grooming claw is generally considered an anthropoid synapomorphy. This study utilizes a quantitative multivariate analysis to define grooming claw morphology and document its presence in platyrrhine monkeys. Our results show that owl monkeys possess grooming claws similar to those of strepsirhines, while titi monkeys possess grooming claw-like morphology. Therefore, we conclude that anthropoids are not clearly united by the absence of a grooming claw. Furthermore, due to their presence in three major primate clades, we infer that it is likely that a grooming claw was present on the second pedal digit of the ancestor of living primates. Therefore, we advise the reassessment of fossil adapids in light of the anatomical correlates described here. This should increase resolution on the homology and polarity of grooming claw morphology, and, therefore, will help provide a sharper picture of primate evolution.
Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of livi... more Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of living anthropoids (monkeys, apes, and humans). Central to this argument is the form of the second pedal digit. Extant strepsirrhines and tarsiers possess a grooming claw on this digit, while most anthropoids have a nail. While controversial, the possible presence of a nail in certain European adapiforms has been considered evidence for anthropoid affinities. Skeletons preserved well enough to test this idea have been lacking for North American adapiforms. Here, we document and quantitatively analyze, for the first time, a dentally associated skeleton of Notharctus tenebrosus from the early Eocene of Wyoming that preserves the complete bones of digit II in semi-articulation. Utilizing twelve shape variables, we compare the distal phalanges of Notharctus tenebrosus to those of extant primates that bear nails (n = 21), tegulae (n = 4), and grooming claws (n = 10), and those of non-primates that bear claws (n = 7). Quantitative analyses demonstrate that Notharctus tenebrosus possessed a grooming claw with a surprisingly well-developed apical tuft on its second pedal digit. The presence of a wide apical tuft on the pedal digit II of Notharctus tenebrosus may reflect intermediate morphology between a typical grooming claw and a nail, which is consistent with the recent hypothesis that loss of a grooming claw occurred in a clade containing adapiforms (e.g. Darwinius masillae) and anthropoids. However, a cladistic analysis including newly documented morphologies and thorough representation of characters acknowledged to have states constituting strepsirrhine, haplorhine, and anthropoid synapomorphies groups Notharctus tenebrosus and Darwinius masillae with extant strepsirrhines rather than haplorhines suggesting that the form of pedal digit II reflects substantial homoplasy during the course of early primate evolution.
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Papers by Stephanie A Maiolino