Advantages and Limitations in the Use of Extant Xenarthrans (Mammalia) as Morphological Models for Paleobiological Reconstruction

Nutrient foramina are small openings in the periosteal surface of the mid-shaft region of long bones that traverse the cortical layer and reach the medullary cavity. They are important for the delivery of nutrients and oxygen to bone tissue and are crucial for the repair and remodeling of bones over time. The nutrient foramina in the femur's diaphysis are related to the energetic needs of the femur and have been shown to be related to the maximum metabolic rate (MMR) of taxa. Here, we investigate the relationship between nutrient foramen size and body mass as a proxy to the aerobic capacity of taxa in living and extinct xenarthrans, including living sloths, anteaters, and armadillos, as well as extinct xenarthrans such as glyptodonts, pampatheres, and ground sloths. Seventy femora were sampled, including 20 from extant taxa and 50 from extinct taxa. We obtained the blood flow rate (Q̇) based on foramina area and performed PGLS and phylogenetic ANCOVA in order to explore differences among mammalian groups. Our results show that, among mammals, taxa commonly associated with lower metabolism like living xenarthrans showed relatively smaller foramina, while the foramina of giant extinct xenarthrans like ground sloths and glyptodonts overlapped with non-xenarthran placentals. Consequently, Q̇ estimations indicated aerobic capacities comparable to other placental giant taxa like elephants or some ungulates. Furthermore, the estimation of the MMR for fossil giant taxa showed similar results, with almost all taxa showing high values except for those for which strong semi-arboreal or fossorial habits have been proposed. Moreover, the results are compatible with the diets predicted for extinct taxa, which indicate a strong consumption of grass similar to ungulates and in contrast to the folivorous or insectivorous diets of extant xenarthrans. The ancestral reconstruction of the MMR values indicated a lack of a common pattern for all xenarthrans, strongly supporting the occurrence of low metabolic rates in extant forms due to their particular dietary preferences and arboreal or fossorial habits. Our results highlight the importance of considering different evidence beyond the phylogenetic position of extinct taxa, especially when extinct forms are exceptionally different from their extant relatives. Future studies evaluating the energetic needs of giant extinct xenarthrans should not assume lower metabolic rates for these extinct animals based solely on their phylogenetic position and the observations on their extant relatives.

Xenarthrans stand out among mammals for various reasons, one of them being their musculoskeletal postcranial specializations. Extant armadillos, anteaters, and sloths feature archetypical adaptations to digging and/or diverse arboreal lifestyles. Numerous extinct xenarthrans dramatically depart in size and morphology from their extant relatives, which has sparked functional interpretations since the end of the eighteenth century. Here, we review the diverse methodological approaches that have been used to investigate functional aspects of the postcranial musculoskeletal system in extant and extinct xenarthrans. Specifically, we address qualitative and quantitative bone morphology (including geometric morphometrics), body size and allometry, bone inner structure, myology, as well as in vivo, ex vivo, and in silico experimentation. Finally, a short account is given on those analyses that included xenarthrans to gain insight into primate anatomy. This review helped to identify potential future directions for the functional analysis of the xenarthran anatomy, a tradition over two centuries old.

The utility of orthodentine microwear analysis as a proxy for dietary reconstruction in xenarthrans (tree sloths, armadillos) was quantitatively and statistically accessed via low-magnification stereomicroscopy. Features such as number of scratches and pits, as well as presence of gouges, hypercoarse scratches, > four large pits, > four cross scratches, and fine, mixed or coarse scratch texture were recorded in 255 teeth from 20 extant xenarthran species. Feature patterns are consistent with scar formation through abrasional (tooth–food) and attritional (tooth–tooth) contact. Number of scratches is the most dietary diagnostic microwear variable for xenarthrans, with herbivorous sloths characterized by > ten scratches and nonherbivorous armadillos by < ten scratches. Discriminant function analysis differentiated arboreal folivores (sloths) and frugivore-folivores (sloths) both from each other and from fossorial carnivore-omnivores (armadillos) and insectivores (armadillos). Microwear patterns in carnivore-omnivores and insectivores are difficult to distinguish between; armadillo microwear may reflect a fossorial lifestyle (grit consumption) rather than primary diet. Cabassous centralis is anomalous in its microwear signal relative to all other insectivores. To test the utility of orthodentine microwear analysis as an indicator of palaeodiet in extinct xenarthrans, microwear in the ground sloth Nothrotheriops shastensis was quantitatively and statistically compared to microwear in extant taxa. Microwear patterns in N. shastensis are most comparable to extant folivores based on scratch number and hierarchical cluster analysis. This strongly supports an herbivorous diet for N. shastensis that is corroborated by multiple independent lines of evidence. Thus, orthodentine microwear analysis can be used to reconstruct diet in extinct xenarthrans.

Overkill and the North American archaeological record—not guilty by association? A comment on Wolfe and Broughton (2020)

A wide range of anthropogenic disturbances accompanied the spread of European settlement across Australia after 1788. They included widespread land clearance, changed fire regimes, harvesting/persecution of native biota, hydrological change through damming and irrigation, and the introduction of new species (Lunney et al. 1997; Calver et al. 1998 and included references). In concert, these changes have contributed to the extinction of 17 mammalian species (Recher & Lim 1990), representing over 6% of the original mammalian fauna and about half of mammal extinctions worldwide in the last 200 years (Dickman et al. 1993). It seems unlikely that the situation has stabilized, because over 17% of extant Australian mammal species have suffered range reductions since colonization (Dickman et al. 1993). Garkaklis et al. (1998, 2000) highlighted that the extinct mammals included many burrowers and diggers, so a suite of species involved in soil turnover, nutrient cycling, and plant propagule dispersal have disappeared. The disruption of such critical processes in the face of anthropogenic stressors is a critical tenet of health theory and suggests a loss of health in the as a whole (Costanza et al. 1998; Rapport 1998a,b). Recent experimental evidence confirmed the significant role of the invasive predators the red fox (Vulpes vulpes) and feral house cat (Felis catus) in the decline of several extant mammals (e.g., Kinnear et al. 1998; Risbey et al. 1999; Risbey et al. 2000 and, by implication, in the extinction of related species. Control of invasive predators is now a major part of recovery plans for a range of Australian mammals (Maxwell et al. 1996), primarily by baiting with the toxin sodium monofluoroacetate (commonly referred to as compound 1080, pronounced 'ten-eighty') (see Twigg & King 1991 for a major review). However, wildlife advocates are often uneasy about poisoning campaigns, so delicate public relations issues are involved (Calver & King 1986; Temple 1990; Marks et al. 2000). Cancers in human health are a tempting metaphor for the destruction wrought by invasive vertebrates to health (Robert Colona, quoted in Stokstad 2000; Stone 2000. In the case of cancers, there is evidence that physiological or psychosocial distress may depress immune system function and contribute to the onset of disease. Malignant cells then proliferate and may disperse, disrupting normal functioning and causing death. Similarly, anthropogenic disturbances may predispose to invasion by alien species, which displace indigenous species or modify processes and disrupt health. Furthermore, the metaphor can be extended to embrace treatments for cancer, with the use of toxins to eradicate or control invasive species seen as for ecosystems. Several authors have explored the parallel between human health and health (e.g., Ehrenfeld 1995; Rapport 1998a. Others have noted the power of such metaphors to encourage community involvement in environmental issues (O'Laughlin 1996; Calver 2000). In this paper, we extend the concept of the human health/ecosystem health metaphor as an educational tool, using the Australian case study of controlling destructive invasive predators by poison baiting. The destructive invasive species can be regarded as cancer cells in the and the poison baiting as to eradicate or contain them. The metaphor may allay community disapproval of poisoning as a control method by relating it to a familiar form of medical treatment used to protect human health. We develop the metaphor by: (1) overviewing the nature of human cancers and the applications, side effects, and limitations of human (2) overviewing characteristics of species introductions and the applications and limitations of chemical control of invasive species, with special reference to predator control in Western Australia as an example of ecosystem chemotherapy; (3) assessing the validity of the ecosystem chemotherapy metaphor by applying it to a range of and commenting on its potential in community education. The discussion reveals that the for ecosystems metaphor is robust in some cases and has potential as an educational tool. It is especially useful in highlighting the value of prevention, as opposed to cure, in the case of invasive species and emphasizing the importance of allowing local communities to make decisions about local health.

Bone and tooth microstructure in extinct and extant mammals and implications for growth and life history evolution, with an emphasis on cervids as a case study

SEARCHING ECOMORPHOLOGICAL PATTERNS SHARED BY EXTANT UNGULATES AND EXTINCT XENARTHRANS. The scarce number of extant representatives of the Order Xenarthra offers a poor idea of the large morphological diversity that existed in the past. Because of this, the interpretation of the ecology of those extinct species is problematic. In order to understand the relationship between diet and habitat, the variability of the lower jaw of different mammals (mainly ungulates and xenarthrans) is analysed in this work by means of geometric morphometric methods. Using principal component and discriminant analyses, the main objective of this contribution is to find taxon-free ecomorphological patterns, which could be applied to extinct xenarthrans with the aim of inferring their ecology. Most part of the variance is due to the phylogenetic factor. However, part of the variability can be interpreted in ecological terms. Because of their characteristic craniodental morphology, glyptodonts occupy their own particular area of the morphospace. Vassallia maxima is proposed as a mix-feeder of mixed habitats, which agrees with previous results. For those sloth species which lower jaw is more similar to that of ungulates, discriminant analysis renders similar results to those obtained in the literature. On the contrary, sloth species with a more different morphology show results more coherent with previous studies by means of principal component analysis. The discriminant functions are not suitable to infer habitat in the Pleistocene mylodontids. Because ruminant species have a mandibular angle proportionally more developed for all diets, discriminant functions are not totally independent of phylogeny.

The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

Sexual conflict - opposite reproductive/genetic interests between sexes - can be a significant driver of insect evolution. Scorpionflies (Insecta: Mecoptera) are models in sexual conflict research due to their large variety of mating practices, including coercive behaviour and nuptial gift provisioning. However, the role of palaeontology in sexual conflict studies remains negligible, namely due to the paucity of well-preserved fossils. Here, we describe three male scorpionflies from Cretaceous and Eocene ambers. The structure of notal and postnotal organs is analysed in extant and extinct forms; a depression below the base of the notal organ in different panorpid species spatially matches the anterior fold of the female's wing. Based on disparate abdominal configurations and correlations in extant relatives, we posit that each new fossil taxon had a different mating approach along a nuptial gifting-coercive spectrum. The Eocene specimen possesses extreme female clamping abdominal armature, suggesting a degree of sexual coercion greater than in any other known scorpionfly, extinct or extant. The fossil record of abdominal modifications in male scorpionflies documents a relatively late evolution (Eocene) of long notal organs indicating oppressive behaviour toward a female during mating. Our findings reveal a wider array of mating-related morphological specialisations among extinct Panorpoidea, likely reflecting more diversified past mating strategies and behaviours in this group, and represent first steps towards gaining a deep-time perspective on the evolution of sexual conflict over mating among insects.

From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms.

Mastigitae comprise most unusual ant-like stone beetles, showing intriguing morphological characters and ecological adaptations. The largest adults among Scydmaeninae can be found in this group; some reaching nearly 9 mm in length, but there are also adults as small as 1.10 mm. Members of Leptomastacini are microphthalmous and depigmented; Mastigini are often black or contrastingly bicolored and have diurnal life style, adults of some species climbing bushes and trees. Papusini inhabit the driest North American deserts and are active during the warmest time of the year; other taxa live in subtropical forests; some are known to enter caves. Adults of some genera have enigmatic modifications of maxillary palps, postgenae or antennae, whose functions still remain unknown. In one genus the male genitalia are enormously elongate, so that these beetles have evolved a method of copulation not known in any other Coleoptera. The evolutionary history of Mastigitae is documented by fossils since the Upper Cretaceous, and extinct forms are even more 'extreme' in their spiny antennae and unusually elongate appendages than their extant relatives. Although phylogenetic hypotheses have been proposed to clarify the relationships and classification of Mastigitae, morphological structures of most genera remain undescribed. They are reviewed in the present synopsis, with detailed descriptions and illustrations of adult structures of all extant genera (Ablepton, Leptomastax, Taurablepton, Mastigus, Palaeostigus, Stenomastigus, Leptochromus, Clidicus and Papusus), with a brief review of known larval forms and fossils. Novel ecological data are given, with emphasis on habitat preferences and feeding behavior. The 'springtail trap' hypothesis for the spiny antennae of Mastigini is rejected, based on field observations and laboratory experiments. For the first time, details of feeding for Palaeostigus and Leptomastax are described. A checklist of species is given, and the main problems related to the classification, phylogeny and ecology of Mastigitae are discussed.

Sexual conflict – opposite reproductive/genetic interests between sexes – can be a significant driver of insect evolution. Scorpionflies (Insecta: Mecoptera) are models in sexual conflict research due to their large variety of mating practices, including coercive behaviour and nuptial gift provisioning. However, the role of palaeontology in sexual conflict studies remains negligible, namely due to the paucity of well-preserved fossils. Here, we describe three male scorpionflies from Cretaceous and Eocene ambers. The structure of notal and postnotal organs is analysed in extant and extinct forms; a depression below the base of the notal organ in different panorpid species spatially matches the anterior fold of the female’s wing. Based on disparate abdominal configurations and correlations in extant relatives, we posit that each new fossil taxon had a different mating approach along a nuptial gifting-coercive spectrum. The Eocene specimen possesses extreme female clamping abdominal armature, suggesting a degree of sexual coercion greater than in any other known scorpionfly, extinct or extant. The fossil record of abdominal modifications in male scorpionflies documents a relatively late evolution (Eocene) of long notal organs indicating oppressive behaviour toward a female during mating. Our findings reveal a wider array of mating-related morphological specialisations among extinct Panorpoidea, likely reflecting more diversified past mating strategies and behaviours in this group, and represent first steps towards gaining a deep-time perspective on the evolution of sexual conflict over mating among insects.

AimBirds have recently undergone a major extinction event which apparently is ongoing. According to some estimates, humans have caused the extinction of up to 20% of the entire avian species diversity since the latter part of the Pleistocene. Few attempts, however, were made to determine how many extinctions are actually known, rather than projected to have occurred. We aimed to quantify the known avian extinctions and assess the relevance of factors thought to have promoted their extinctions, that is, large size, flightlessness and insularity.LocationGlobal.TaxonAves.Materials and MethodsWe collected data on bird extinctions from the literature. We recorded the geographic range, flight ability and body size of each species. If mass data were unavailable, we estimated them from linear measurements using machine learning tools. We modelled masses of extinct birds on those of extant ones and estimated the effects of taxonomy, body mass, insularity and flight ability.ResultsWe have identified 469 species of birds that humans, directly or indirectly, drove to extinction. These extinctions have predominantly occurred on islands. Extinct birds were often flightless. We estimated the body mass of 291 extinct species and found that overall, the median mass of extinct species was seven times larger than that of extant ones. Extinctions mostly occurred in families of large‐bodied birds, whilst lineages of small birds have fared better. Insular birds are overall larger than mainland birds, a trend that becomes even more evident when the extinct forms are analyzed. However, within lineages, sizes are only slightly larger on islands than on continents.Main conclusionsOur findings suggest that extinct bird species differed from extant birds by being larger, mostly restricted to islands, and often flightless. These factors made them especially vulnerable to human prosecution and to other anthropogenically related declines. Our modern understanding of birds is skewed with respect to the nature of avian faunas that existed before the current wave of human‐induced extinctions changed our world forever.

The preparation of allometric equations generally uses multiple linear regression equations. The use of this regression equation is usually not carried out through various tests but goes directly to the t test and F test stages. Therefore, this paper aims to provide an example of determining the regression equation through the classical assumption test stages. Makila (Litsea angulata BI) was chosen as an example because it provides environmental services, especially in dealing with climate change and has not been widely studied. The research method used is a quantitative method. Destructive sampling was taken and the material used consisted of 40 young Makila plants planted in polybags next to the greenhouse at the Faculty of Agriculture, Pattimura University, Ambon. The diameter of each sample was measured from the ground surface to a height of 5 cm and numbered 1 to 40. After being coded, the plant samples were cut down and all young trees were divided into stem segments, branches, twigs, leaves and roots. The root segments were collected carefully to facilitate their separation from the soil in polybags. The parts of the roots that still contain soil are cleaned with a machete and brush until they are free of soil and other dirt. Next, each segment was weighed for its wet weight (in g) and dry weight, thus enabling the determination of the biomass content (in g) for each segment. Data analysis was carried out using the Multiple Linear Regression Equation method. The regression model was examined for normality and suitability in predicting independent variables, ensuring there were no issues with multicollinearity, heteroscedasticity, and autocorrelation. The results of the normality test showed that the significance value for the remaining data was 0.813 &gt; 0.05, indicating normal distribution. TThe results of the multicollinearity test show that there is no multicollinearity problem, this is indicated by the VIF value of the two independent variables (tree diameter and tree height each 1.049) &lt; 10 and the Tolerance value (tree diameter and tree height 0.953 each) &gt; 0.100. The results of the heteroscedasticity test show that the two independent variables have a significance value of more than 0.05. The results of the autocorrelation test show the Durbin Watson (DW) value = 1.956 with a range of 1.65 – 2.35 which means there is no correlation problem. The results yielded a multiple linear regression: Y = -1131.146 + 684.799X1 + 4.276X2, where Y is biomass, X1 is the diameter, and X2 is the tree height. Based on the results of the t-test: variable X1 partially affected Y while variable X2 partially had no effect on Y. The F-test indicated that variables X1 and X2 jointly affected Y with R Square: 0.919 or 91.9% and the rest was influenced by other unexplored factors. To simplify biomass prediction and field measurement, a regression equation that used only 1 independent variable, namely tree diameter, was used for the experiment. Allometric equation only used 1 variable, Y = - 1,084,626 + 675,090 X1, where X1 = tree diameter, Y = Total biomass with R = 0.957, and R square = 0.915. The regression equation for young Makila plant provides assurance that the regression equation obtained is accurate in estimation, unbiased and consistent. This is because in data processing classical assumptions have been tested. This equation can save time, costs and energy, as well as make measurements easier in the field so that future researchers can develop allometric equations in other plants for efficiency.

Animal vocalization is broadly recognized as ecologically and evolutionarily important. In mammals, hyoid elements may influence vocalization repertoires because the hyoid apparatus anchors vocal tissues, and its morphology can be associated with variation in surrounding soft-tissue vocal anatomy. Thus, fossil hyoid morphology has the potential to shed light on vocalizations in extinct taxa. Yet, we know little about the hyoid morphology of extinct species because hyoid elements are rare in the fossil record. An exception is found in the Rancho La Brea tar pits in Los Angeles, California, where enough hyoids have been preserved to allow for quantitative analyses. The La Brea Tar Pits and Museum houses one of the largest and most diverse collections of carnivore fossils, including hyoid elements from the extinct felids Smilodon fatalis and Panthera atrox. Here, we found that extant members of Felinae (purring cats) and Panthera (roaring cats) showed characteristic differences in hyoid size and shape that suggest possible functional relationships with vocalization. The two extinct taxa had larger and more robust hyoids than extant felids, potentially reflecting the ability to produce lower frequency vocalizations as well as more substantial muscles associated with swallowing and respiration. Based on the shape of the hyoid elements, Panthera atrox resembled roaring cats, while Smilodon fatalis was quite variable and, contrary to suggestions from previous research, more similar overall to purring felids. Thus P. atrox may have roared and S. fatalis may have produced vocalizations similar to extant purring cats but at a lower frequency. Due to the confounding of vocalization repertoire and phylogenetic history in extant Felidae, we cannot distinguish between morphological signals related to vocalization behavior and those related to shared evolutionary history unrelated to vocalization.