Apparent sixth sense in theropod evolution: The making of a Cretaceous weathervane.

OBJECTIVE: Two separate and distinctive skills are necessary to find prey: Detection of its presence and determination of its location. Surface microscopy of the dentary of albertosaurines revealed a previously undescribed sensory modification, as will be described here. While dentary "foramina" were previously thought to contain tactile sensory organs, the potential function of this theropod modification as a unique localizing system is explored in this study. METHOD: Dentary surface perforations were examined by surface epi-illumination microscopy in tyrannosaurine and albertosaurine dinosaurs to characterize their anatomy. Fish lateral lines were examined as potentially comparable structures. RESULT: In contrast to the subsurface vascular bifurcation noted in tyrannosaurines (which lack a lateral dentary surface groove), the area subjacent to the apertures in albertosaurine grooves has the appearance of an expanded chamber. That appearance seemed to be indistinguishable from the lateral line of fish. CONCLUSION: Dentary groove apertures in certain tyrannosaurid lines (specifically albertosaurines) not only have a unique appearance, but one with significant functional and behavior implications. The appearance of the perforations in the dentary groove of albertosaurines mirrors that previously noted only with specialized neurologic structures accommodating derived sensory functions, as seen in the lateral line of fish. The possibility that this specialized morphology could also represent a unique function in albertosaurine theropods for interacting with the environment or facilitating prey acquisition cannot be ignored. It is suggested that these expanded chambers function in perceiving and aligning the body relative to the direction of wind, perhaps a Cretaceous analogue of the contemporary midwestern weathervane.

Bejel: acquirable only in childhood?

Bejel clearly has a long history in the Middle East and the Sudan, but was it transmitted to Europe? As the major manifestation of bejel is presence of periosteal reaction in 20-40% of afflicted populations, absence of significant population frequency of periosteal reaction in Europe would exclude that diagnosis. Examination of skeletal populations from continental Europe revealed no significant periosteal reaction at the time of and immediately subsequent to the Crusades. Thus, there is no evidence for bejel in Europe, in spite of clear contact (the mechanism of bejel transmission in children) between warring groups, at least during the Crusades. This supports the hypothesis that bejel is a childhood-acquired disease and apparently cannot be contracted in adulthood.

Making tracks: the forensic analysis of footprints and footwear impressions.

Analysis of footwear characteristics, impressions, and track ways can provide important evidence in a crime scene investigation. In this article, we present examples of how students can be involved in hands-on laboratory-based activities as a means of introducing the forensic sciences. The teaching methodology employs active learning strategies that allow students to discover scientific principles for themselves, develop techniques of critical thinking and problem solving, and gain appreciation for how knowledge arises. By including forensic sciences in the science curriculum, students develop an appreciation for the interrelatedness of all the sciences. From this series of activities, i.e., examining analyses of footprint and footwear impressions, students working as teams will gather information, analyze data, and draw conclusions. Moreover, students will be able to assess the significance of the quality and variability in the data collection process as well as learn the value of controls and experimental design through comparison of results with other groups.

Chewing through the Miocene: an examination of the feeding musculature in the ground sloth Hapalops from South America (Mammalia: Pilosa).

Hapalops, a smaller-sized and early sloth of the Megatheroidea, appeared in the middle Miocene Santa Cruz formation of Argentina. This genus is part of the group from which later, larger megatheroids arose, i.e., Nothrotheriops and Megatherium. Many cranial characters support this idea; however Hapalops is not merely a smaller antecedent of the later forms. Specifically, Hapalops retains short anterior caniniform teeth, and a temporomandibular joint elevated above the cheek tooth row; a combination distinct among sloths. An elevated temporomandibular joint occurs in Bradypus, a tree sloth with anterior chisel-shaped teeth instead of caniniforms, and the tree sloth Choloepus, which is aligned with the megalonychids, has anterior caniniforms. Hapalops has an elongated zygomatic ascending process that is reminiscent of that in Bradypus; however, the Bradypus skull is extremely foreshortened while that of Hapalops is elongated, as in nothrotheres, but not deepened as in megatheres. Previous work identified many sloth cranial character complexes, and functional limitations on skull feature combinations. The unique Hapalops character patterns indicate a selective feeder with a mediolaterally oriented grinding stroke during mastication.

The power of the claw.

Scratches on bones have routinely been attributed to tooth marks (a predominantly untested speculation), ignoring the effects of claws, perhaps because of the general assumption that claws are too soft to damage bone. However, some pathologies appears to be more compatible with claw rather than tooth impacts. Therefore, it is critical to determine if the claws of any animal are capable of scratching into the surface of any bone--a test and proof of concept. A tiger enrichment program was used to document actual bone damage unequivocally caused by claws, by assuring that the tiger had access to bones only by using its paws (claws). The spectrum of mechanisms causing bone damage was expanded by evidentiary analysis of claw-induced pathology. While static studies suggested that nails/claws could not disrupt bone, specific tiger enrichment activities documented that bones were susceptible to damage from the kinetic energy effect of the striking claw. This documents an expanded differential consideration for scratch marks on bone and evidences the power of the claw.

Comparative analysis of paw pad structure in the clouded leopard (Neofelis nebulosa) and domestic cat (Felis catus).

The Clouded leopard (Neofelis nebulosa) is a medium-sized highly arboreal cat. This study compares the structure of the digital, metacarpal and metatarsal pads of the manus and pes in N. nebulosa to that of the domestic cat (Felis catus). Covered by a stratified squamous cornified epithelium, the pads have a supple deposit of subepidermal fat that is partitioned by collagen fibers and extensively anchored to the muscle tendon sheaths. In both animals, a pes metatarsal pad suspensory ligament originates from the Mm. flexores digitorum profundi tendon and forms 3-4 small branches that project through the dermal fat layer and attach to the pad epidermis. In the cat manus, four tendons of equal size extend from the M. flexor digitorum superficialis (FDS) to form the manica flexoria in digits 2-4 from which extends a metacarpal pad suspensory ligament (MPSL) on digits 2 and 5 that extends into the tela subcutanea and epidermis. On digits 3 and 4 MPSL extends directly from the FDS tendon itself. In contrast, manus FDS tendons 1 and 5 in N. nebulosa were thin and either project directly to the tela subcutanea (tendon 1) or connect with the manica flexoria forming a metacarpal pad suspensory ligament (tendon 5). Tendons 2-4 connect with the manica flexoria from which MPSL project into the tela subcutanea and epidermis. In both species, the suspensory ligaments may serve to contract the pad to conform to the under lying substrate, thus enhancing the animal's ability to grip branches while climbing.

Forelimb myology of the pygmy hippopotamus (Choeropsis liberiensis).

Based on morphological analyses, hippos have traditionally been classified as Suiformes, along with pigs and peccaries. However, molecular data indicate hippos and cetaceans are sister taxa (see review in Uhen, 2007, this issue). This study analyzes soft tissue characters of the pygmy hippo forelimb to elucidate the functional anatomy and evolutionary relationships of hippos within Artiodactyla. Two specimens from the National Zoological Park in Washington, D.C. were dissected, revealing several adaptations to an aquatic lifestyle. However, these adaptations differ functionally from most aquatic mammals as hippos walk along river or lake bottoms, rather than swim. Several findings highlight a robust mechanism for propelling the trunk forward through the water. For example, mm. pectoralis superficialis and profundus demonstrate broad sites of origin, while the long flexor tendons serve each of the digits, reflecting the fact that all toes are weight-bearing. Pygmy hippos also have eight mm. interossei and a well-developed m. lumbricalis IV. Retention of intrinsic adductors functions to prevent splaying of the toes, an advantageous arrangement in an animal walking on muddy substrates. Published descriptions indicate common hippos share all of these features. Hippo and ruminant forelimbs share several traits; however, hippos are unique among artiodactyls in retaining several primitive muscles (e.g., mm. palmaris longus and flexor digitorum brevis). These findings are consistent with the hypothesis that hippos diverged from other Artiodactyla early in the history of this group. Additional analyses of hindlimb and axial muscles may help determine whether this trajectory was closely allied to that of Cetacea.

Bone manifestations of actinomycosis.

Actinomycosis, originally classified as a fungus, is now considered a branching bacteria. Although jaw involvement often presents with classic pathognomonic signs, postcranial disease has not been so characterized. Affected bones from individuals diagnosed in life with actinomycosis were macroscopically and radiologically examined for their macroscopic character. The bones were riddled with spheroid, occasionally coalescing defects associated with periosteal reaction. Erosion penetrated cortical bone as readily as through cortical bone or subchondral bone. X-ray revealed circular lesions with a slight sclerotic margin. Actinomycosis apparently has unique features, which should allow it to be distinguished from multiple myeloma (because of presence of reactive new bone formation) and from fungal disease (because of lack of "fronts of resorption" and penetrating spicules). Similarity to fungal infection is especially of interest because of the earlier phylogenetic classification question.

Assessing behavior in extinct animals: was Smilodon social?

It has been suggested that saber-tooth species such as Smilodon fatalis were social because partially healed skeletal injuries were found at Rancho La Brea, California. This conclusion assumes injured animals would die without help. This paper will rebut assertions of sociality. First, cats use metabolic reserves to heal quickly without feeding. Second, dehydration is a more profound limitation than starvation as prey carcasses only provide a quarter of necessary water. Injured animals must be mobile enough to find water or die of dehydration. Their presence in a tar pit also strongly suggests locomotion. Finally, the relatively small brain found in Smilodon is not consistent with sociality. Another argument for sociality has been the large ratio of Smilodon to other species in the La Brea tar pits. However, the remains of a non-social species, the Golden eagle (Aquila chrysaetus), are about as common as Smilodon. Contrariwise, the highly social grey wolf (Canis lupus) and coyote (Canis latrans) are extremely rare. Available evidence does not support sociality in Smilodon.