Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology最新文献

Measurement error (ME) in geometric morphometrics has been the subject of countless articles, but none specific to the effect of time lags on landmark digitization error. Yet, especially for visiting scientists working on museum collections, it is not uncommon to collect data in multiple rounds, with interruptions of weeks or years. To explore the impact of time lags on Procrustes shape analysis, I repeatedly digitized the same landmarks, on photographs of crania of adult yellow-bellied marmots, at progressively longer time intervals, ranging from a few hours to days, weeks and, in one case, many years. Using a battery of methods, I found that there is indeed a time-related systematic ME suggesting the possibility of a “visiting scientist effect” biasing shape patterns. However, the relationship between time lags and the magnitude of the bias is not simple and linear, but complex. Interestingly, the impact of the bias on the results of tests of sexual dimorphism and allometry is modest, and mostly negligible, unless the design of the data collection is highly unbalanced. When this happens, as in a simulated case where females are digitized first and males only later (or vice versa), the effect of the bias on tests of biological variation becomes important and can even lead to opposite conclusions on group differences. I will discuss when systematic ME in landmark data is more problematic and how to try to mitigate the impact of a potential “visiting scientist effect” on shape analyses.

Certain microphagous fishes possess an epibranchial organ (EBO), a paired muscular pocket-like structure in the posterior pharynx, that facilitates the aggregation of small food items entering the oropharyngeal cavity. Morphologically complex and phylogenetically diverse, the anatomy of EBOs has been described in a small number of taxa that possess this structure, in many cases without a thorough investigation at the microscopic and ultrastructural level. Additionally, the evolution of EBOs has not been rigorously examined within a phylogenetic comparative context, leaving many unanswered questions about how the morphological diversity of EBOs relates to historical patterns and ecology. We characterized the anatomy, histological architecture, and structural patterns of EBOs in 13 otomorphan species belonging to the orders Clupeiformes, Gonorynchiformes, and Characiformes; this sampling includes Cetengraulis edentulus, Nematalosa come, and Tenualosa thibaudeaui, in which the presence of an EBO has not been previously documented. We then conducted a preliminary investigation of relationships between otomorphan EBO anatomy, phylogeny, and diet. Patterns of anatomical diversity were best explained by variation along five morphological axes: shape, size, associated gill rakers, muscularity, and adiposity. EBOs consisted of bilaterally paired diverticula surrounded by layers of circumferential and longitudinal muscle and varying amounts of adipose tissue. Papillae were found in the epithelium lining the diverticulum of each organ; they varied in length and width along the proximodistal axis of the diverticulum and were studded with mucus-producing cells. We found that EBO anatomy was not strongly correlated with phylogenetic relatedness but was moderately correlated with diet in some instances. We hypothesize that EBOs have independently evolved in Otomorpha multiple times via a conserved developmental pathway that makes use of the same underlying tissue types to construct morphologically diverse structures. These findings suggest that there are multiple ways to build an EBO using the same basic anatomical components to achieve the same functional goal—the aggregation of small prey.

Facial expression is a key component of primate communication, and primates (including humans) have a complex system of facial musculature underpinning this behavior. Human facial musculature is highly variable across individuals, but to date, whether other primate species exhibit a similar level of inter-individual variation is unknown. Whether individual-level variation in facial musculature covaries with significant differences in facial movement within the same individual is also unknown. Here, we use facial dissection data from 31 adult rhesus macaques, the largest sample to date, to quantify inter-individual variation in facial muscle presence. We used a subsample of eight individuals to measure covariation between facial muscle presence and the presence of external facial movements (action units in the Facial Action Coding System, or FACS). We found, in contrast to humans, limited inter-individual variation in muscle presence, but the zygomatic region exhibited more gross anatomical variation in muscle presence and morphology than any other region of the macaque face. We also found a good correspondence between facial muscle presence and the presence of the associated action units. Our results indicate that the observed variation in rhesus macaque facial expressivity is not likely driven primarily by variation in facial muscle presence but may instead be due to other factors such as learned behavior and/or physiological differences. These findings provide insight into the anatomical basis of inter-individual variation in facial behavior in primates and suggest potential differences in variation between humans and other primate species.

This special volume, “New Paleontological Research in Turtles and other Vertebrates”, pays tribute to the Spanish Researcher Dr. Emiliano Jiménez Fuentes, who passed away in December 2021. His role was fundamental for the development of the studies on the vertebrate faunas of the Spanish Eocene Duero Basin, as well as for the creation of the Collection of Fossil Vertebrates of the Duero Basin (“Sala de las Tortugas” of the University of Salamanca), which houses more than 25,000 specimens of vertebrates, including about 20 holotypes of mammals and reptiles. Since 1960 and over several decades, Dr. Jiménez Fuentes was the leading researcher in the study of Iberian fossil turtles. Fourteen scientific articles on various topics, related to his extensive professional career, are part of this volume. Representatives of several lineages of reptiles and mammals from the Duero Basin are analyzed, from systematic perspectives, but also considering other aspects of their paleobiology. Among them, a new eusuchian crocodyliform (i.e., Asiatosuchus oenotriensis) and a new hyaenodontid mammal (i.e., Prodissopsalis jimenezi) are included. Taxa from other ages and geographic regions, but with systematic affinities with those deposited in the “Sala de las Tortugas,” are analyzed in other articles of this volume. Given the great interest of Dr. Jiménez Fuentes in the evolutionary history of Testudinata, several papers analyze members of this lineage, including the description of a new giant tortoise from the Miocene of Germany (i.e., Titanochelon schleichi), and that of a new marine cryptodire from Portugal (i.e., Lusochelys emilianoi).

Available paleontological evidence, although scarce, points to the early diversification of salientian lissamphibians in the Triassic and Early Jurassic. This study provides new key anatomical information on the earliest mostly articulated frog currently known, thereby improving our understanding of the early evolution of this lissamphibian lineage. Herein, available specimens of the Early Jurassic Vieraella herbstii from Patagonia, which consist of dorsal and ventral imprints of the incomplete, partially articulated skeleton of a single individual, are thoroughly redescribed. Although we comment on its known features, we focus on those that had been misinterpreted or overlooked previously. Among other features, we address the relative proportions of the skull regions and limbs, the morphology of the vomers, the peculiar articulation of the palatine flanges of premaxilla and maxilla that suggests the presence of well-developed cristae subnasales, and the presence of prepollex. The most surprising, significant findings are the presence of stapes, indicating the possibility of a complete tympanic middle ear, and of a short, tapering urostyle and postsacral vertebral elements. Based on available information, we present partial reconstructions of the pectoral girdle and the skeleton of Vieraella in the dorsal aspect. Discussion of the evolutionary significance of these features and perusal of the phylogenetic and functional analyses that included Vieraella in the taxon sampling highlight the necessity of thorough revision of the scorings and measurements, incorporating information presented herein. This reassessment will be relevant not only to clarify its relationships but also to provide sound insights into the early diversification of frogs.

The crania of leporid lagomorphs are uniquely fenestrated, including the posterior cranial bones and the lateral portion of the maxilla. The functional significance of the highly fenestrated rostrum has received considerably little attention, despite being absent in other mammalian herbivores with a long rostrum. This unique feature is of particular interest when considering functional relationships between the loading regime and cranial structure. Two primary hypotheses have been suggested: maxillary fenestrations may be associated with the transmission and redirection of incisal occlusal forces, or fenestrations may reduce skull weight to assist with maneuverability and increase running speed. Here we apply a comparative approach using finite element analysis to determine how the overall stress and strain environment is affected by the presence or absence of maxillary fenestrations. We compare three lagomorph species with various degrees of latticing in the fenestrated rostrum with two macropods that do not have fenestrations. We then produce theoretical models of the three lagomorphs by filling in the fenestrated region. Our results show that the presence of fenestrations makes little difference to the overall stress experienced through the cranium and does not impact the efficiency of incisor biting. This adds to the increasing evidence that features of lagomorph cranial morphology correlate with locomotor demands, adapting to loads other than mastication. Modulating cranial mass with fenestrations may provide the benefits of a lighter skull while still providing enough surface area for muscle attachments.

The vertebral column consists of multiple homologous elements that have specialized within and between taxa and serve important functions in positional support and as protection for the central nervous system. The study of modularity and integration provides new insights into the evolution of complex structures such as the vertebral column. Patterns of modularity and integration may reflect underlying genetic-developmental patterns and facilitate evolution. Previous studies have identified mixed modularity patterns within and between elements across mammals generally, within primates and carnivorans. Here, we assess modularity within and between elements in the complete post-axial vertebral column in four catarrhine taxa: Macaca (n = 96), Hylobates (n = 77), Pan (n = 92), and Homo (n = 151). We use the Covariance Ratio (CR) to estimate r² and the standardized eigenvalues (SVE) variance for comparative purposes. Our results show that there is general, widespread integration within the catarrhine vertebral column, both within and between elements. Hominoids tend to display greater modularity than do macaques, but these estimates are rarely significant. Clusters of modularity in the mid-cervical and upper thoracic regions may relate to special nervous system structures in these areas, and locomotor behaviors in general may influence patterns of modularity in primates. In particular, we find that size is a pervasive factor affecting integration among vertebral elements, though its effects on specific structures are variable. Our results generally do not agree with those found across mammals or within carnivorans, and future studies should focus on genus-level assessments across a variety of taxa.

The Early Pleistocene fossil site of Schernfeld, a karst fissure filled with an ossiferous breccia, is well known due to the abundant fossil remains, mainly of micromammals and carnivores. Since the discovery, the taxonomic status of the Schernfeld mustelids has caused controversy and, consequently, various authors have listed different species. Until recently, none of these species has been the subject of adequate studies. A detailed revision of the Schernfeld mustelids material was made through comparative morphology based on mustelids from other European Early and early Middle Pleistocene sites. It reveals the presence of five mustelids: Gulo gulo schlosseri, Martes vetus, Meles meles, Mustela palerminea, and Mustela praenivalis. Their remains are characterized by ancestral features, especially in M. vetus, M. palerminea, and M. praenivalis. Due to the morphology of mustelids and the taxonomical composition of the Schernfeld fauna, the biochronological age of the entire assemblage was re-evaluated and assessed for ca. 1.9–1.7 mya.

Primates are often considered to have a poor sense of smell. While all studies identify small olfactory bulbs (OB; the region of the brain responsible for processing scent) among haplorhines, whether or not strepsirrhines also possess small OBs is less clear, as is the evolutionary backdrop from which these patterns emerged. Here, we examine the relative size of the olfactory bulbs in cranial endocasts of living and fossil primates and their kin (Euarchontoglires [Primates, Dermoptera, Scandentia, Rodentia, Lagomorpha]), testing previous hypotheses. Regression analyses of OB volume and mass relative to endocranial volume (ECV) and body mass (BM), and ANOVAS of residuals, were performed on a dataset of 181 extant and 41 extinct species. Analyses show clear differences in the relative size of the OBs, with haplorhines possessing distinctly smaller OBs relative to all other clades. Pairwise tests indicate haplorhine OBs are significantly smaller than those of all other clades, including strepsirrhines; when the haplorhines are removed from analyses, strepsirrhines are significantly smaller than all other clades. This suggests that a reduction in OB size occurred at the crown primate node, a pattern also seen in ancestral state reconstruction (ASR) analyses. The ASR analyses suggest multiple iterations of olfactory bulb size decrease occurred in Haplorhini, reflecting large amounts of parallelism. These results likely differ from previous studies due to the inclusion of additional fossils and more appropriate outgroups based on up-to-date phylogenetic hypotheses.