The organ of vision morphology of the southern two-toed sloth (Choloepus didactylus Linnaeus, 1758; Pilosa, Choloepodidae).

The Choloepus didactylus is a species belonging to the Choloepodidae family of the Folivora suborder. This study concerns the anatomical, morphometrical, histological and histochemical examination of the eye tunics, eyelids and orbital glands in the three adult Choloepus didactylus coming from the Wroclaw Zoological Garden. The cornea consists of four layers since Bowman's membrane was absent. The presence of palisades of Vogt formed from 14/15 to 20/21 layers of epithelial cells was demonstrated. Macroscopically, the tapetum lucidum was not identified, while degenerative choroidal tapetum lucidum cellulosum was found microscopically. The ciliary muscle was found with our histological approach. The pupil was round in shape (post-mortem). The presence of tarsal glands has not been demonstrated in both eyelids. The conjunctiva-associated lymphoid tissue (CALT) has been shown in the upper and lower eyelids. The superficial gland of the third eyelid produced a seromucous secretion. The third eyelid was shaped like a curved arch and composed of hyaline cartilage. The deep gland of the third eyelid was big and multilobar acinar simple with serous character. The lacrimal gland produced mucous secretion. The results of our research indicate that the features of the eye anatomy in the southern two-toed sloth (C. didactylus) are also typical of the Folivora suborder and have common features and differences with Vermilingua.

Auditory brainstem responses in the nine-banded armadillo (Dasypus novemcinctus).

The auditory brainstem response (ABR) to tone burst stimuli of thirteen frequencies ranging from 0.5 to 48 kHz was recorded in the nine-banded armadillo (Dasypus novemcinctus), the only extant member of the placental mammal superorder Xenarthra in North America. The armadillo ABR consisted of five main peaks that were visible within the first 10 ms when stimuli were presented at high intensities. The latency of peak I of the armadillo ABR increased as stimulus intensity decreased by an average of 20 µs/dB. Estimated frequency-specific thresholds identified by the ABR were used to construct an estimate of the armadillo audiogram describing the mean thresholds of the eight animals tested. The majority of animals tested (six out of eight) exhibited clear responses to stimuli from 0.5 to 38 kHz, and two animals exhibited responses to stimuli of 48 kHz. Across all cases, the lowest thresholds were observed for frequencies from 8 to 12 kHz. Overall, we observed that the armadillo estimated audiogram bears a similar pattern as those observed using ABR in members of other mammalian clades, including marsupials and later-derived placental mammals.

DISEASES OF THE GIANT ANTEATER (MYRMECOPHAGA TRIDACTYLA) IN CAPTIVITY: STUDY OF MEDICAL DATA FROM 99 INDIVIDUALS IN EUROPEAN ZOOS.

The giant anteater (Myrmecophaga tridactyla) is one of the three species in the family Myrmecophagidae of the suborder Vermilingua. It is the only species of the genus Myrmecophaga. The species, subject to increasing threats in its natural environment, is classified as vulnerable on the International Union for the Conservation of Nature Red List of Threatened Species. European zoos are involved in the ex situ conservation of the giant anteater, which is essential for its long-term viability. However, the diseases encountered by European captive populations of giant anteaters are not well documented, and best practice guidelines are not yet available for the species. An online two-part survey was conducted among European institutions hosting or having housed anteaters over a 20-yr period concerning the current management of captive populations and the diseases encountered. Medical data were collected from 99 giant anteaters from 30 institutions. Among the study population, 4% of the individuals were born in the wild and 96% were born in captivity. Seventy animals (71%) were still alive at the time of data collection, with an average age of 8 yr. A predominance of digestive (20%), dermatologic (20%)-with mainly wounds-and internal parasitism (18%) disorders was observed, followed by behavioral (13%), musculoskeletal (12%), respiratory (11%), nutritional (10%), and ocular (9%) disorders. Mortality mainly concerns the most extreme age categories: very young individuals, mostly secondary to trauma, and older individuals with no main cause identified. This paper details all the medical conditions reported in the European captive giant anteaters included in the study. It allows us to formulate some medical and zootechnical recommendations for the species management and to envisage new research perspectives.

Molecular detection of piroplasmids in mammals from the Superorder Xenarthra in Brazil.

Xenarthra mammals can be found from southern North America to southern South America, including all Brazilian biomes. Although it has been shown that Xenarthra mammals can play a role as reservoirs for several zoonotic agents, few studies investigate the diversity of piroplasmids (Apicomplexa: Piroplasmida) in this group of mammals. Taking into account that piroplasmids can cause disease in animals and humans, understanding the prevalence and diversity of piroplasmids in Xenarthra mammals would contribute to conservation efforts for this group of animals as well as to infer risk areas for transmission of emergent zoonosis. The present study aimed to investigate the occurrence and molecular identity of piroplasmids in free-living mammals of the Superorder Xenarthra from four Brazilian states (Mato Grosso do Sul, São Paulo, Rondônia, and Pará). For this, DNA was extracted from blood or spleen samples from 455 animals. A nested PCR based on the 18S rRNA gene was used as screening for piroplasmids. Of the 455 samples analyzed, 25 (5.5%) were positive. Additionally, PCR assays based on 18S rRNA near-complete, cox-1, cox-3, hsp70, cytB, ß-tubulin genes and the ITS-1 intergenic region were performed. Five out of 25 positive samples also tested positive for ITS-1-based PCR. The phylogenetic analysis positioned three 18S rRNA sequences detected in Priodontes maximus into the same clade of Babesia sp. detected in marsupials (Didelphis albiventris, Didelphis marsupialis, and Monodelphis domestica) and Amblyomma dubitatum collected from opossums and coatis in Brazil. On the other hand, the 18S rRNA sequence obtained from Dasypus novemcinctus was closely related to a Theileria sp. sequence previously detected in armadillos from Mato Grosso State, grouping in a subclade within the Theileria sensu stricto clade. In the phylogenetic analysis based on the ITS-1 region, the sequences obtained from Myrmecophaga tridactyla and Tamandua tetradactyla were placed into a single clade, apart from the other piroplasmid clades. The present study demonstrated the molecular occurrence of Piroplasmida in anteaters and Babesia sp. and Theileria sp. in armadillos from Brazil.

New paleopathological findings from the Quaternary of the Brazilian Intertropical Region expand the distribution of joint diseases for the South American megafauna.

OBJECTIVE: To evaluate pathological changes in fossils from the Brazilian Intertropical Region (BIR), expanding the records of previously reported diseases for representatives of the Quaternary South American megafauna, including taxa not studied in previous works. MATERIALS AND METHODS: We carried out a thorough macroscopic analysis of fifteen unpublished specimens belonging to representatives of the Quaternary megafauna of BIR to identify evidence of pathological alterations. RESULTS: Alterations included: osteophytes in Toxodontidae, Megatheridae and E. laurillardi; rough subchondral bone, bone overgrowth and bone erosion in E. laurillardi; slit-shaped subchondral depressions in Equidae and E. laurillardi; and a triangular-shaped porous lesion in Mylodontidae. CONCLUSIONS: The alterations found allowed the recognition of the first cases of osteoarthritis for Toxodontidae and articular depressions for Equidae, and new cases of both diseases in Eremotherium laurillardi; a new case of osteochondritis dissecans for Mylodontidae; potential new cases of calcium pyrophosphate deposition and spondyloarthropathy for E. laurillardi SIGNIFICANCE: Our results provide additional evidence that calcium pyrophosphate deposition disease was widely spread among species of the South American megafauna and suggest that osteochondritis dissecans may have been relatively common among ground sloths. LIMITATIONS: The identification of calcium pyrophosphate deposition and spondyloarthropathy in E. laurillardi are quite tentative because the evidence found is ambiguous and the number of examined specimens is limited.

Taxonomic notes on the ant-eating spider genera Asceua Thorell, 1887 and Cydrela Thorell, 1873 from India, with comment on Indian species of Euryeidon Dankittipakul & Jocqué, 2004 (Araneae: Zodariidae).

Indian species of the ant-eating spider genera Asceua Thorell, 1887, Cydrela Thorell, 1873 and Euryeidon Dankittipakul & Jocqué, 2004 are reviewed. The species Asceua cingulata (Simon, 1905) is redescribed and illustrated based on type and freshly collected material and a new species, A. thrippalurense sp. nov. is described and illustrated based on both sexes. All the Indian Cydrela species are transferred back to the genus Capheris Simon, 1893 under which these were originally placed. The species Capheris escheri Reimoser, 1934 comb. rest. and Caph. stillata Simon, 1905 comb. rest. are redescribed and illustrated, the former based on its type specimen, while the latter based on freshly collected material. The species Capheris nitidiceps Simon, 1905 comb. rest. is considered as a nomen dubium due to the immature stage of the holotype. The two Indian species of Euryeidon are transferred to the genus Laminion Sankaran, Caleb & Sebastian, 2020 due to generic similarities. The distribution of all these species is mapped.

Evidence of artefacts made of giant sloth bones in central Brazil around the last glacial maximum.

The peopling of the Americas and human interaction with the Pleistocene megafauna in South America remain hotly debated. The Santa Elina rock shelter in Central Brazil shows evidence of successive human settlements from around the last glacial maximum (LGM) to the Early Holocene. Two Pleistocene archaeological layers include rich lithic industry associated with remains of the extinct giant ground sloth Glossotherium phoenesis. The remains include thousands of osteoderms (i.e. dermal bones), three of which were human-modified. In this study, we perform a traceological analysis of these artefacts by optical microscopy, non-destructive scanning electron microscopy, UV/visible photoluminescence and synchrotron-based microtomography. We also describe the spatial association between the giant sloth bone remains and stone tools and provide a Bayesian age model that confirms the timing of this association in two time horizons of the Pleistocene in Santa Elina. The conclusion from our traceological study is that the three giant sloth osteoderms were intentionally modified into artefacts before fossilization of the bones. This provides additional evidence for the contemporaneity of humans and megafauna, and for the human manufacturing of personal artefacts on bone remains of ground sloths, around the LGM in Central Brazil.

Metastatic Sertoli cell tumour in a captive giant anteater (Myrmecophaga tridactyla).

There are a few studies on diseases of anteaters, but reports on reproductive lesions and neoplasms of these animals are scarce. This is the first report of a case of metastatic Sertoli cell tumour in a giant anteater (Myrmecophaga tridactyla). The animal had renal lesions associated with impaired renal function as indicated by serum biochemistry. Histopathological and immunohistochemical examinations provided a conclusive diagnosis of Sertoli cell tumour with metastasis to the liver, kidneys and lymph nodes.

High Trypanosoma cruzi prevalence in armadillo (Zaedyus pichiy; Xenarthra: Chlamyphoridae) populations from Mendoza, Argentina.

Armadillos are considered important reservoir hosts for Trypanosoma cruzi, the causative agent of Chagas disease. The first report of T. cruzi infection in pichis (Zaedyus pichiy), a small armadillo species endemic to central Argentina and Chile, dates back to 1935. However, more recent reports on T. cruzi in this species are scarce. The objective of this study was to assess T. cruzi infection and parasite load in Z. pichiy from Mendoza Province, an area endemic to human Chagas disease. Blood samples were obtained in 2014-2016 from pichis from Lavalle (low Monte), Malargüe (Patagonian steppe), and San Carlos (ecotone) departments, Mendoza Province, Argentina. The detection and quantification of T. cruzi was performed through qPCR amplification using satellite primers. Of the 265 analyzed samples, 201 (76%) were positive for T. cruzi. Parasite loads varied between < 0.1-55.8 parasite-equivalents/mL (par-eq/mL), with a median of 1.1 par-eq/mL in quantifiable samples. The prevalence was similar in Malargüe and Lavalle (85-94%), but significantly lower in pichis from San Carlos (50%). Animals from Lavalle captured after hibernation had significantly higher parasite loads (median 2.0 par-eq/mL). In Malargüe, T. cruzi infection and parasite loads were significantly lower before than after hibernation in 2016. The high prevalence and low median parasite load suggest a chronic and persistent infection of T. cruzi in pichis. Regional differences and a marked increase in precipitation during 2015-2016 could have influenced annual and seasonal infection rates of this vector-borne disease.

Nereididae (Annelida: Phyllodocida) from intertidal macroalgae in Western Australia.

The last extensive exploration of Nereididae diversity within coastal waters of Western Australia was done in 1975-1984. We collected Nereididae associated with macroalgae from 38 rocky intertidal shores of Western Australia (18°S to 34°S). Eighteen species belonging to seven genera are described and illustrated. Two new species, Nereis edentata n. sp. and Nereis yuedensis n. sp., were found. Nereis edentata n. sp. differs from other Nereis species having one row of paragnaths on Areas VII-VIII and smooth notopodial homogomph falcigers in posterior chaetigers. Nereis yuedensis n. sp. differs from other Nereis species having one row of paragnaths on Areas VII-VIII and notopodial homogomph falcigers with at least one large lateral tooth, and also species having notopodial homogomph falcigers starting from chaetiger 3. The distribution of N. yuedensis n. sp. was found to be restricted within temperate Australia and N. edentata n. sp. appears to be transitional between temperate and tropical regions. Also, we remove from synonymy the probable Western Australian endemic species, Pseudonereis rottnestiana (Augener, 1913), and provide a key to all known genera and species of Nereididae from Western Australian waters.

Macroscopic and histological aspects of the pharynx and larynx of the giant anteater (Myrmecophaga tridactyla Linnaeus, 1758).

Giant anteater (Myrmecophaga tridactyla) is an endangered species that resides in much of Latin America, but it has been losing its habitat, especially in the Cerrado biome, where it constantly suffers traumas resulting from fires and roadkill. The anatomical knowledge of structures of the respiratory system is important for a better morphophysiological understanding of the species. Thus, this study aimed to perform the macroscopic and histomorphological description of the pharynx and larynx of the giant anteater. Twelve adult giant anteaters were used, three of them fixed in buffered formalin for further dissection and pharynx and larynx macroscopic analysis of structures. From the other animals, samples of the pharynx and larynx were collected and prepared for histological evaluation under optical microscope. Macroscopically, their pharynx and soft palate are extensive, and the anatomical location of these structures and the larynx differs greatly from that described in other species. The larynx, although more caudal, was similar to that of other animals. Histologically, the epithelium of these regions varied between the pseudostratified ciliated columnar and the non-keratinized stratified squamous epithelium. Laryngeal cartilages were composed of elastic (epiglotti) and hyaline cartilages (arytenoid, cricoid and thyroid cartilage), with an ossification process and glandular clusters around the hyaline cartilage. The distinct anatomical location of the pharynx and larynx of Myrmecophaga tridactyla is the main macroscopic finding of this study, besides the length of the pharynx and soft palate of these animals.

Age-related changes in antioxidant defenses of the Mediterranean centipede Scolopendra cingulata (Chilopoda).

The activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and glutathione S-transferase (GST), as well as the concentrations of sulfhydryl (SH) groups and glutathione (GSH) were analyzed in five age classes of the Mediterranean centipede Scolopendra cingulata as follows: embryo, adolescens, maturus junior, maturus, and maturus senior. The data obtained showed the presence of SOD, CAT, GSH-Px, GR, GST, and SH groups in embryos. The transition from embryo to adolescens was accompanied by an increase in the activities of all studied enzymes, in response to the increased production of ROS due to the increased metabolic activity of the centipede associated with growth and development. Our results show that trends in antioxidant enzyme (AOE) activities were not uniform among adult age classes, suggesting that maturus junior, maturus, and maturus senior differentially respond and/or have different susceptibility to ROS. On the other hand, GSH concentration in embryos was undetectable, highest in adolescens and decreased in the latter part of life. Pearson correlation analysis in embryos showed that the activities of the AOEs were strongly and positively correlated with each other but negatively correlated with GSH and SH groups. At later age classes, SOD, CAT, GSH-Px, GR, GSH, and SH groups were no longer significantly correlated with GST. In the discriminant analysis, the variables that separated the age classes were GR, GST, SH groups, and body length. Body length was directly related to the age of individuals, clearly indicating that development/aging affects the regulation of antioxidant defense in this species.

Three toes and three modes: Dynamics of terrestrial, suspensory, and vertical locomotion in brown-throated three-toed sloths (Bradypodidae, Xenarthra).

Living sloths exhibit numerous anatomical specializations towards inverted quadrupedalism, however, previous studies have noted a more varied locomotor repertoire than previously anticipated. In this study, we present spatiotemporal gait characteristics and triaxial kinetic data from the brown-throated three-toed sloth (Bradypus variegatus) across three locomotor modes: terrestrial quadrupedal "crawling", suspensory walking, and vertical climbing. Compared to quadrupedal crawling and suspensory walking, B. variegatus adopted longer contact times and stride durations, larger duty factors, and greater speed during vertical climbing. Net fore-aft impulses were significantly greater during vertical climbing in both limb pairs than in quadrupedal crawling and suspensory walking. Functionally, during quadrupedal crawling and vertical climbing, both limb pairs served propulsive roles, while differentiation between a propulsive forelimb and braking hindlimb was observed during suspension. Net tangential forces differentiated vertical climbing kinetics from the other modes of locomotion, with the introduction of bidirectional pulling and pushing forces in the forelimb and hindlimb, respectively. The net mediolateral impulses were similar in vertical climbing and quadrupedal crawling as both limb pairs directed forces in one direction, whereas during suspensory walking, the laterally dominant forelimb was opposed by the medially dominant hindlimb. In total, this study provides novel data on the diverse locomotor dynamics in a slow-moving arboreal tetrapod and posits new testable hypotheses about the neuroplasticity and ease of transitioning between locomotor behaviors. The strikingly similar kinetic profiles of quadrupedal crawling and suspensory walking compared to vertical climbing suggest shared neuromuscular and mechanical demands between these mirrored locomotor modes.

Trypanosoma cruzi Survey in Poached Pichis (Zaedyus pichiy; Mammalia, Cingulata) from Mendoza, Argentina.

The transmission cycles of Trypanosoma cruzi, the causative agent of Chagas disease, include a wide variety of mammals and hematophagous triatomine insects. Infection with this blood parasite has been confirmed in many armadillo species; however, information on infection in Zaedyus pichiy, a small armadillo that inhabits areas endemic to Chagas disease, is scarce. Our objective was to determine the infection frequency and parasite load of T. cruzi in 49 wild Z. pichiy confiscated dead from poachers in Mendoza, Argentina, 2010-2017. We detected T. cruzi DNA in 32 of 49 armadillos (65%) using real-time PCR, confirming infection with T. cruzi in a high proportion of confiscated pichis. No differences were found related to sex, age, or ecoregion origin of the assessed pichis. Parasite loads ranged between <0.1 and 8.88 parasite equivalents/microgram cardiac tissue. Additional studies on the infection status of Z. pichiy are needed to determine their role in the maintenance of the sylvatic transmission cycle and the potential zoonotic risk from hunted pichis.

RABIES DIAGNOSIS AND RESPONSE TO VACCINATION IN SOUTHERN TAMANDUA (TAMANDUA TETRADACTYLA).

Rabies has rarely been described in Xenarthra, and rabies vaccine response has not been documented. A southern tamandua (Tamandua tetradactyla) presented with nonspecific clinical signs and was euthanatized. Subsequently, immunohistochemistry and RT-PCR confirmed a rabies diagnosis. Following these tests, a group of eight captive tamanduas were vaccinated with a killed rabies vaccine, and titers were measured at the time of vaccination and 23 d later. One animal had day 0 titers suggestive of previous vaccination or exposure. All animals had detectable neutralizing rabies virus antibody titers after vaccination, but one animal failed to meet the World Organization for Animal Health's definition for adequate vaccination (≥0.5 IU/ml), and two other animals had low antibody titers (0.56 and 0.6 IU/ml). Rabies should be considered as a possible cause of illness in tamanduas, and rabies vaccination may be a useful preventative measure when anthropic interaction through medical care or ambassador roles is occurring.

Free-ranging Southern anteater mating behavior: Contribution to Tamandua natural history.

Observing behavior in wild Southern Anteaters (Tamandua tetradactyla) allows Xenarthran researchers to gain perspective on natural history of this neotropical scansorial species. We describe the use of the prehensile tail to facilitate copulation for a pair in southeastern Brazil, a novel observation for this species. This detailed account of mating behavior in lesser anteaters is one of very few in the literature and contributes to basic knowledge of this group.

Cranial osteology of a juvenile specimen of Acratocnus ye (Mammalia, Xenarthra, Folivora) and its ontogenetic and phylogenetic implications.

The present study comprises a description of the skull and jaw anatomy of a juvenile specimen of the Antillean sloth Acratocnus ye, from the Holocene of Haiti. Detailed descriptions and illustrations are provided of the skull bones and their sutural connections, which normally fuse in adults. Descriptions are also provided for the mandible and ear ossicles, as well as endocranial surfaces and sinuses exposed by breaks. The anatomy of our juvenile A. ye is compared to that of adult A. ye to assess ontogenetic changes in the skull. Several of these ontogenetic features are significant new observations that impact the relationships within Xenarthra as a whole, or between Xenarthrans and other placental mammals, most notably, the presence of a separate mesethmoid element, the presence of alveoli for a lower deciduous canine and anterior incisor, and the presence of separate rostral and caudal entotympanic elements. A full list of such changes are provided. In addition, the specimen provides information on phylogenetically relevant characters, including features unique to the genus Acratocnus, and features of the clade Choloepodini, including Acratocnus, the smaller extinct Antillean sloth Neocnus, and the extant two-toed sloth Choloepus. Contrary to previous studies, Acratocnus shares as many features with Choloepus as it does with its fellow Antillean form Neocnus in the present study, which is consistent with current morphology-based phylogenetic hypotheses regarding the relationships within Choloepodini. The current study highlights the need for further anatomical and phylogenetic investigations of Antillean sloths (Megalocnidae/Megalonychidae), and juvenile sloths in general.

Ex Situ Approaches for the Conservation of Genetic Resources in the Superorder Xenarthra.

Xenarthra-a superorder of placental mammals endemic to the Neotropics-is represented by armadillos, anteaters, and sloths. Considering their long history in the Americas, extant xenarthrans represent an important group for understanding the impact of past environmental changes on species diversification and serve key ecological functions as ecosystem engineers. Unfortunately, most wild xenarthran populations are at risk, due primarily to anthropogenic activities, necessitating urgent conservation efforts. Moreover, the paucity of information on some species has rendered population estimation and, consequently, conservation management challenging. In addition, relatively few groups are researching this superorder, perhaps because fieldwork with armadillos, anteaters, or sloths and their captive care are challenging tasks. Nevertheless, dedicated research and efforts to ensure the long-term conservation of these animals are deemed essential. In this context, cryobanks are a practical approach for breeding and maintaining genetic diversity in wildlife, and they are important tools for assisting and improving both ex situ and in situ conservation strategies. Therefore, cryopreservation of biological resources may be a promising strategy for conserving xenarthrans. Specifically, semen cryopreservation, which has already been applied in some species, may be the most effective strategy for this group. The present article provides an overview of ex situ conservation of xenarthrans, which will contribute to the development and implementation of additional strategies for protecting these unique mammals.

Computed tomography and anatomy of the abdominal structures in the giant anteater (Myrmecophaga tridactyla).

The giant anteater (Myrmecophaga tridactyla) is the largest of the Neotropical vermilinguans. This animal is the second mammal most frequently run over on the roads of Cerrado biome, Brazil. Therefore, it is pivotal to know the anatomy of this species to contribute to the clinical care of these animals. Thus, the aim of this study was to identify the anatomical structures in the abdominal region of the giant anteater using computed tomography (CT). For this, the tomographic analysis was performed in sequential order in the craniocaudal direction in five giant anteaters. Moreover, four giant anteater corpses were used for anatomical studies, where two corpses were sectioned in cross sections of approximately 3 cm each, and two animals were dissected to identify the abdominal organs. The association between CT and anatomical study allowed the visualization of anatomical structures found in the abdominal cavity, such as the topographic anatomy facilitates the identification of organs on CT images. The findings of this study demonstrated that CT is a good technique to provide detailed information about the anatomical structures in the abdominal cavity and that this study can be used as CT and anatomical reference for veterinarians who care for wild animals.

Morphology of the brain base arteries of the giant anteater (Myrmecophaga tridactyla)

This study aimed to describe the brain base arteries of the Myrmecophaga tridactyla using ten cadavers of adults from this species, including five male and five female specimens. The arterial vascular bed was perfused via the thoracic aorta with a dyed natural latex solution, and the animals were fixed and preserved with a 10% formaldehyde buffered solution. The encephala were removed, and their vessels dissected. Basilar artery formation occurred by anastomosis of the thick ventral spinal artery with vertebral arteries. The basilar artery formed two arterial islands and gave bulbar and pontine branches, and cranial, middle, and caudal cerebellar arteries and ended by forking into its terminal branches, the caudal communicating arteries. The blood supply of the encephalon derived solely from the vertebrobasilar system, and the arterial circle of the brain was closed caudally and rostrally. The absence of participation of internal carotid arteries in encephalon irrigation, the island formations by the basilar artery, and the fusiform shape of the arterial circle of the brain are peculiar characteristics of the vascular anatomy of the brain base of M. tridactyla.