Sciurid Rodents Research Articles

The macroevolutionary dynamics of activity pattern in mammals: Primates in context

Activity pattern has played a prominent role in discussions of primate evolutionary history. Most primates are either diurnal or nocturnal, but a small number are active both diurnally and nocturnally. This pattern—cathemerality—also occurs at low frequency across mammals. Using a large sample of mammalian species, this study evaluates two macroevolutionary hypotheses proposed to explain why cathemerality is less common than diurnality and nocturnality: 1) that cathemeral lineages have higher extinction probabilities (differential diversification) and 2) that transitions out of cathemerality are more frequent, making it a less persistent state (differential state persistence). Rates of speciation, extinction, and transition between character states were estimated using hidden-rates models applied to a phylogenetic tree containing 3013 mammals classified by activity pattern. The models failed to detect consistent differences in diversification dynamics among activity patterns, but there is strong support for differential state persistence. Transition rates out of cathemerality tend to be much higher than transition rates out of nocturnality. Transition rates out of diurnality are similar to those for cathemerality in most clades, with two important exceptions: diurnality is unusually persistent in anthropoid primates and sciurid rodents. These two groups combine very low rates of transition out of diurnality with high speciation rates. This combination has no parallels among cathemeral lineages, explaining why diurnality has become more common than cathemerality in mammals. Similarly, the combination of rates found in anthropoids is sufficient to explain the low relative frequency of cathemerality in primates, making it unnecessary to appeal to high extinction probabilities in cathemeral lineages in this clade. These findings support the hypothesis that the distribution of activity patterns across mammals has been influenced primarily by differential state persistence, whereas the effect of differential diversification appears to have been more idiosyncratic.

Geology and lithology of the Tagay-1 section at Olkhon Island (Lake Baikal, Eastern Siberia), and description of Aplodontidae, Mylagaulidae and Sciuridae (Rodentia, Mammalia)

Excavations along the Tagay-1 section shed light into the composition of small mammal assemblages of the Tagay site. The present paper focuses on the geology and geomorphology of Olkhon Island, the lithology and fossil evidence along the Tagay-1 section and descriptions of the aplodontid, mylagaulid and sciurid rodents. The described fossils are isolated teeth of four taxa, Ansomys sp. (Aplodontidae), Lamugaulus olkhonensis Tesakov and Lopatin, 2015 (Mylagaulidae), Sciuridae indet. and Spermophilinus debruijni nov. spec. (Sciuridae). The archaic tooth pattern of these rodents suggests an age around the Early/Middle Miocene transition.

Squirreling from Afar: Adapting Squirrel-Net Modules for Remote Teaching and Learning

The shift from face-to-face instruction to remote teaching and learning has proven to be a challenging endeavor for many reasons, including lack of time, resources, and inspiration. Lab courses, the &quot;hands-on&quot; portion of many curricula, may be especially difficult to adapt to online learning given the common use of specialized equipment, materials, and techniques that require close supervision. Without the time and resources to creatively modify existing activities or create new ones, remote lab courses run the risk of becoming less effective, equitable, and/or engaging. Squirrel-Net has created four field-based activities for biology labs that are easy to implement, highly flexible for different course aims, and readily adaptable to a remote learning environment. In this essay, we briefly summarize the modules and propose several ways that each can be adjusted to accommodate online teaching and learning. By providing authentic learning opportunities through distance delivery we hope to promote widespread student engagement and creative solutions for instructors. <em>Primary image</em>:&nbsp;A student-pair collecting behavioral data. One student observes the squirrel while the other keeps track of time and records the behavior remotely. By connecting through a video call, even students without access to squirrels may participate in the activity. Photo by Laurie Dizney. <strong>Additional Squirrel-Net articles:</strong> <ul> <li><a href="https://doi.org/10.24918/cs.2020.26">An Introduction to the Squirrel-Net Teaching Modules</a></li> <li><a href="https://doi.org/10.24918/cs.2020.7">Squirreling Around for Science: Observing Sciurid Rodents to Investigate Animal Behavior</a></li> <li><a href="https://doi.org/10.24918/cs.2020.30">Sorry to Eat and Run: A Lesson Plan for Testing Trade-off in Squirrel Behavior Using Giving Up Densities (GUDs)</a></li> <li><a href="https://doi.org/10.24918/cs.2020.25">Squirrels in Space: Using Radio Telemetry to Explore the Space Use and Movement of Sciurid Rodents</a></li> <li><a href="https://doi.org/10.24918/cs.2020.6">How Many Squirrels Are in the Shrubs? A Lesson Plan for Comparing Methods for Population Estimation</a></li> </ul>

Coccidian Parasites of Flying Squirrels, Glaucomys spp. (Rodentia: Sciuridae), from Alaska and Arkansas, with a Description of a New Species of Eimeria (Apicomplexa: Eimeriidae).

New World flying squirrels, Glaucomys spp., are nocturnal arboreal sciurid rodents that have been previously surveyed for coccidial parasites. To date, 4 species of Eimeria have been reported from 2 species of Glaucomys. Here we report 2 species of eimerians from southern flying squirrels (Glaucomys volans) and the endemic Prince of Wales flying squirrel (Glaucomys sabrinus griseifrons). Oocysts of Eimeria dorneyi Levine and Ivens were found to be passing in the feces of 4 G. s. griseifrons from Alaska and a new species of Eimeria was present in feces from 6 G. volans from Arkansas. Oocysts of Eimeria hnidai n. sp. are ellipsoidal with a bilayered wall, measure 23.7 × 13.7 μm, and have a length/width (L/W) ratio of 1.7; a micropyle and oocyst residuum are absent but polar granule(s) are present. Sporocysts are ellipsoidal-elongate and measure 11.8 × 4.9 μm, L/W 2.2; Stieda body is present but sub-Stieda and para-Stieda bodies are absent. The sporocyst residuum is composed of small indistinct granules along the edge or in the center of the sporocyst. This is the first coccidian reported from G. volans from Arkansas as well as the initial coccidian (E. dorneyi) reported from G. s. griseifrons from Alaska. We also provide a summation of the coccidia known from North American flying squirrels.

Gastro-intestinal helminths in the red-bellied squirrel introduced in Argentina: accidental acquisitions and lack of specific parasites

Introduced species may lose their natural parasites when invading a new habitat, may acquire new, local parasites or may introduce parasites from their native range. We studied the gastro-intestinal helminth fauna associated with the red-bellied squirrel Callosciurus erythraeus (Pallas, 1778) introduced in Argentina to evaluate its role as a host of either specific or acquired parasites in two invasion foci. We analyzed entire digestive tracts of 72 red-bellied squirrels captured in the main invasionfocus(Lujan, provinceofBuenosAires)betweenFebruaryandMay2011, andinasecondary focus (Canada de Gomez, province of Santa Fe) in December 2008. We only found two nematode specimens: an adult male belonging to the genus Pterygodermatites (Paucipectines) Quentin, 1969 and another adult male belonging to the genus Stilestrongylus (Freitas, Lent and Almeida, 1973). None of these genera were previously listed for the red-bellied squirrel in introduced areas, but a species of the genus Pterygodermatites was previously reported for this squirrel in its native habitat. These results indicate that, to date, the red-bellied squirrel in Argentina is accidentally parasitised by nematodes acquired in its new environment and has no specific gastro-intestinal helminths. This could be related with a “founder eect” and/or the lack of sciurid rodents that prevent the red-bellied squirrel to be colonized by pre-adapted helminth taxa. Other factors that may play a role are the small number of mammals with arboreal habits and some “encounter barriers” in the new environment that prevent the acquisition of helminths with a wide host spectrum.

Not all fine-branch locomotion is equal: Grasping morphology determines locomotor performance on narrow supports

Fine-branch models have long played a central role in primate evolutionary research. Nevertheless, recent studies of positional behavior in nonprimate arboreal mammals have challenged the idea that synapomorphic primate features, such as grasping extremities, uniquely facilitated access to the fine-branch zone. We test the alternative hypothesis that grasping extremities specifically improve locomotor performance in a fine-branch environment by examining how support diameter influences locomotor mechanics in one sciurid rodent (Sciurus carolinensis) and two platyrrhine primates (Callithrix jacchus and Saimiri boliviensis). These species were chosen to broadly model different stages in the evolution of primate grasping morphology. The results showed that transitioning from broad to narrower supports required the greatest kinematic adjustment in squirrels and the least adjustment in squirrel monkeys, with marmosets displaying an intermediate level of adjustment. Moreover, on any given support, squirrels' locomotor mechanics differed from marmosets' in a manner consistent with a greater need for stability, despite superficial ecomorphological similarities between sciurid rodents and callitrichine primates. Morphological analyses of autopodial size and proportions suggest that variation in locomotor performance more closely tracked variation in overall hand and foot size rather than digit length per se. Indeed, a broad comparative analysis revealed that for their body mass, primates have longer hands than similarly sized arboreal rodents and marsupials (although only the primate-rodent comparison was significant after incorporating phylogenetic relatedness). Inclusion of fossil stem primates (plesiadapiforms) and euprimates (adapiforms) in these analyses suggests that this primate-wide grade shift in relative autopodial size must have occurred early in the evolutionary history of the group. Overall, our findings show that basal primate morphological adaptations may have specifically facilitated improved locomotor performance in a fine-branch niche, rather than merely permitting access to the environment. As such, future adaptive hypotheses of primate origins should incorporate the import of primate-like morphology on locomotor performance as well.

Experimental study of alarm calls of the oriental tit (Parus minor) toward different predators and reactions they induce in nestlings

AbstractAnti‐predatory strategies of birds are diverse and may include predator‐specific alarm calls. For example, oriental tit (Parus minor) parents can distinguish snakes from other predators and produce snake‐specific referential vocalizations ("jar" call) when a snake poses a threat to their nest. The “jar” call has a very specific function to induce fledging of nestlings close to fledging age. This reaction ensures nestlings' survival in natural encounters with snakes that are capable of entering nest cavities and kill entire broods. Sciurid rodents, like chipmunks, may pose a similar threat to cavity‐nesting birds. We explored the hypothesis that parents use the fledging‐inducing alarm vocalizations in this situation, because chipmunks, like snakes, can kill the brood upon entering the nest cavity. We compared alarm calls of parents toward two predators (chipmunk and snake) who pose a similar threat to the nestlings in a nest cavity, and toward an avian predator (Eurasian jay) who cannot enter nest cavities and poses no threat to the nestlings in a nest. Our results show that the vocal responses of oriental tits were different among the three predators. This suggests that the acoustic properties of vocal responses to predators are different between predators of a similar hunting strategy (nest‐cavity entering). The playback of recorded vocal responses of parents to chipmunks did not trigger the fledging of old nestlings, whereas the vocalizations toward a snake did, as shown by earlier studies. Our study suggests that the vocal response of parents does not carry information about the ability of predators to enter the nest cavity and confirms the special status of alarm calls triggered by snakes.

Squirrels in Space: Using Radio Telemetry to Explore the Space Use and Movement of Sciurid Rodents

Squirrels in Space: Using Radio Telemetry to Explore the Space Use and Movement of Sciurid Rodents

Squirreling Around for Science: Observing Sciurid Rodents to Investigate Animal Behavior

Squirreling Around for Science: Observing Sciurid Rodents to Investigate Animal Behavior

Genetic variation drives seasonal onset of hibernation in the 13-lined ground squirrel

Hibernation in sciurid rodents is a dynamic phenotype timed by a circannual clock. When housed in an animal facility, 13-lined ground squirrels exhibit variation in seasonal onset of hibernation, which is not explained by environmental or biological factors. We hypothesized that genetic factors instead drive variation in timing. After increasing genome contiguity, here, we employ a genotype-by-sequencing approach to characterize genetic variation in 153 ground squirrels. Combined with datalogger records (n = 72), we estimate high heritability (61–100%) for hibernation onset. Applying a genome-wide scan with 46,996 variants, we identify 2 loci significantly (p < 7.14 × 10−6), and 12 loci suggestively (p < 2.13 × 10−4), associated with onset. At the most significant locus, whole-genome resequencing reveals a putative causal variant in the promoter of FAM204A. Expression quantitative trait loci (eQTL) analyses further reveal gene associations for 8/14 loci. Our results highlight the power of applying genetic mapping to hibernation and present new insight into genetics driving its onset.

Seed ingestion and germination in rattlesnakes: overlooked agents of rescue and secondary dispersal.

Seed dispersal is a key evolutionary process and a central theme in the population ecology of terrestrial plants. The primary producers of most land-based ecosystems are propagated by and maintained through various mechanisms of seed dispersal that involve both abiotic and biotic modes of transportation. By far the most common biotic seed transport mechanism is zoochory, whereby seeds, or fruits containing them, are dispersed through the activities of animals. Rodents are one group of mammals that commonly prey on seeds (granivores) and play a critical, often destructive, role in primary dispersal and the dynamics of plant communities. In North America, geomyid, heteromyid and some sciurid rodents have specialized cheek pouches for transporting seeds from plant source to larder, where they are often eliminated from the pool of plant propagules by consumption. These seed-laden rodents are commonly consumed by snakes as they forage, but unlike raptors, coyotes, bobcats, and other endothermic predators which eat rodents and are known or implicated to be secondary seed dispersers, the role of snakes in seed dispersal remains unexplored. Here, using museum-preserved specimens, we show that in nature three desert-dwelling rattlesnake species consumed heteromyids with seeds in their cheek pouches. By examining the entire gut we discovered, furthermore, that secondarily ingested seeds can germinate in rattlesnake colons. In terms of secondary dispersal, rattlesnakes are best described as diplochorous. Because seed rescue and secondary dispersal in snakes has yet to be investigated, and because numerous other snake species consume granivorous and frugivorous birds and mammals, our observations offer direction for further empirical studies of this unusual but potentially important channel for seed dispersal.

Molecular systematics and evolutionary history of catenotaeniid cestodes (Cyclophyllidea)

Phylogenetic relationships, evolutionary history and systematics of tapeworms of the family Catenotaeniidae were studied using nucleotide sequences of the partial 28S nuclear rDNA (ca. 1,500 bp) and mitochondrial 12S–16S DNA (ca. 820 bp) genes. The tapeworm material consists of 29 species, including type species of the genera Catenotaenia Janicki, 1904, Catenotaenioides Haukisalmi, Hardman and Henttonen, 2010, Pseudocatenotaenia Tenora, Mas‐Coma, Murai and Feliu, 1980, Skrjabinotaenia Akhumyan, 1946, Meggittina Lynsdale, 1953, and Hemicatenotaenia Tenora, 1977. The basal phylogenetic structure of the Catenotaeniidae remains unresolved, but it is shown that most of the catenotaeniids in Eurasia and Africa comprise a large clade represented by species of Catenotaenia, Catenotaenioides, Skrjabinotaenia and Meggittina, parasitizing murid, cricetid, nesomyid and sciurid rodents. The results suggest that the divergence and early radiation of this clade have occurred in murid rodents (represented by Apodemus spp. and Mus musculus in the present material) in western Eurasia, followed by colonization of Africa, most likely independently of the colonization of their murid hosts between these continents. There is very little evidence of cophylogeny between hosts and parasites, suggesting that host transfers have played a major role in the divergence of catenotaeniids. In Africa, catenotaeniids have radiated in other murid and nesomyid rodents, and later colonized Madagascar and recolonized Eurasia. The results also show that the subfamily Skrjabinotaeniinae (including Skrjabinotaenia and Meggittina) is monophyletic, but the Catenotaeniinae (including Catenotaenia, Catenotaenioides, Pseudocatenotaenia and Hemicatenotaenia) is clearly non‐monophyletic. In addition, the genera Catenotaenia and Skrjabinotaenia were both found to be non‐monophyletic. Based on the phylogenetic and morphological evidence, several taxonomical changes, mainly new combinations, are proposed. Overall, the present results suggest that the family Catenotaeniidae is in need of major systematic revision.

DNA barcoding of metacestodes found in the Guerlinguetus ingrami (Rodentia: Sciuridae) reveals the occurrence of Hydatigera taeniaeformis sensu stricto (Cyclophyllidea: Taeniidae) in the Americas

The existence of cryptic species in the genus Hydatigera, cyclophillid cestodes, mainly of felids, was recently described based on molecular studies of parasites from Asia, Europe and Africa. However, the occurrence of H. taeniaeformis sensu stricto (s.s.), the species more widely distributed and with a presumed specificity for murid rodents as intermediate hosts, has not been formally described in Americas. In the present study, during necropsy of an Ingram's squirrel specimen, Guerlinguetus ingrami, found dead in the municipality of Belo Horizonte, Minas Gerais state, Brazil, strobilocerci were found in the liver. The metacestodes were subjected to morphological and molecular studies. Sequences of the COI barcode region were obtained and used for phylogenetic analyses. The morphology and measures of the rostellar hooks were compatible with the ones described for H. taeniaeformis s.s. This identification was confirmed by a molecular phylogenetic approach (96.2–99.7% similarity with isolates of the parasite from Europe and Asia). This is the first molecular confirmation of the existence of H. taeniaeformis s.s. on the American continent. Moreover, the involvement of sciurid rodents in the transmission of H. taeniaeformis s.s. is discussed here as a probable case of parasite spillover.

Paltry past‐precipitation: Predisposing prairie dogs to plague?

ABSTRACTThe plague bacterium Yersinia pestis was introduced to California in 1900 and spread rapidly as a sylvatic disease of mammalian hosts and flea vectors, invading the Great Plains in the United States by the 1930s to 1940s. In grassland ecosystems, plague causes periodic, devastating epizootics in colonies of black‐tailed prairie dogs (Cynomys ludovicianus), sciurid rodents that create and maintain subterranean burrows. In doing so, plague inhibits prairie dogs from functioning as keystone species of grassland communities. The rate at which fleas transmit Y. pestis is thought to increase when fleas are abundant. Flea densities can increase during droughts when vegetative production is reduced and herbivorous prairie dogs are malnourished and have weakened defenses against fleas. Epizootics of plague have erupted frequently in prairie dogs during years in which precipitation was plentiful, and the accompanying cool temperatures might have facilitated the rate at which fleas transmitted Y. pestis. Together these observations evoke the hypothesis that transitions from dry‐to‐wet years provide conditions for plague epizootics in prairie dogs. Using generalized linear models, we analyzed a 24‐year dataset on the occurrence of plague epizootics in 42 colonies of prairie dogs from Colorado, USA, 1982–2005. Of the 33 epizootics observed, 52% erupted during years with increased precipitation in summer. For the years with increased summer precipitation, if precipitation in the prior growing season declined from the maximum of 502 mm to the minimum of 200 mm, the prevalence of plague epizootics was predicted to increase 3‐fold. Thus, reduced precipitation may have predisposed prairie dogs to plague epizootics when moisture returned. Biologists sometimes assume dry conditions are detrimental for plague. However, 48% of epizootics occurred during years in which precipitation was scarce in summer. In some cases, an increased abundance of fleas during dry years might compensate for other conditions that become less favorable for plague transmission. Global warming is forecasted to amplify the hydrological cycle in the Great Plains, causing an increased occurrence of prolonged droughts interceded by brief periods of intense precipitation. Results herein suggest these changes might affect plague cycles in prairie dogs. Both negative and positive consequences of dry conditions should be considered when managing plague. © 2017 The Wildlife Society.

A review of the flea genus Phalacropsylla Rothschild, 1915 (Siphonaptera, Ctenophthalmidae, Neopsyllinae, Phalacropsyllini) with new host and distributional records.

A redescription of the genus Phalacropsylla Rothschild is provided. Six species are recognized: Phalacropsylla allos Wagner, P. hamata Tipton and Mendez, P. morlani Eads and Campos, P. nivalis Barrera and Traub, P. oregonensis Lewis and Maser, and P. paradisea Rothschild. Phalacropsylla hamata is designated herein as a junior synonym of P. paradisea. The distribution of P. paradisea is more extensive than previously thought, extending from Arizona through southern Colorado, into New Mexico, Texas, and northern Mexico (State of Nuevo León). It is the least host-specific of all species of Phalacropsylla, occurring on 13 different host species including cricetid, heteromyid, murid, and sciurid rodents and several carnivores, although it most commonly occurs on Neotoma albigula Hartley. The range of P. oregonensis is expanded from eastern Oregon to southeastern Idaho. Numerous records are documented for the most common and ubiquitous species, P. allos, which is found in British Columbia, central to northern California, Idaho, Montana, Colorado, Nevada, Utah, Wyoming, Arizona, and New Mexico. Neotoma cinerea Ord is the principal host of P. allos. Phalacropsylla allos is a winter flea west of the Rocky Mountains, but it has been reported in warmer months of the year on the eastern slopes of the Rocky Mountains in Larimer County, Colorado. A distribution map and key are provided for all species in the genus Phalacropsylla.

The Beaver\u2019s Phylogenetic Lineage Illuminated by Retroposon Reads

Solving problematic phylogenetic relationships often requires high quality genome data. However, for many organisms such data are still not available. Among rodents, the phylogenetic position of the beaver has always attracted special interest. The arrangement of the beaver’s masseter (jaw-closer) muscle once suggested a strong affinity to some sciurid rodents (e.g., squirrels), placing them in the Sciuromorpha suborder. Modern molecular data, however, suggested a closer relationship of beaver to the representatives of the mouse-related clade, but significant data from virtually homoplasy-free markers (for example retroposon insertions) for the exact position of the beaver have not been available. We derived a gross genome assembly from deposited genomic Illumina paired-end reads and extracted thousands of potential phylogenetically informative retroposon markers using the new bioinformatics coordinate extractor fastCOEX, enabling us to evaluate different hypotheses for the phylogenetic position of the beaver. Comparative results provided significant support for a clear relationship between beavers (Castoridae) and kangaroo rat-related species (Geomyoidea) (p < 0.0015, six markers, no conflicting data) within a significantly supported mouse-related clade (including Myodonta, Anomaluromorpha, and Castorimorpha) (p < 0.0015, six markers, no conflicting data).

Virtual endocast of the early Oligocene Cedromus wilsoni (Cedromurinae) and brain evolution in squirrels.

Extant squirrels exhibit extensive variation in brain size and shape, but published endocranial data for living squirrels are limited, and no study has ever examined brain evolution in Sciuridae from the perspective of the fossil record to understand how this diversity emerged. We describe the first virtual endocast for a fossil sciurid, Cedromus wilsoni, which is known from a complete cranium from Wyoming (Orellan, Oligocene), and make comparisons to a diverse sample of virtual endocasts for living sciurids (N = 20). The virtual endocasts were obtained from high-resolution X-ray micro-computed tomography data. Comparisons were also made with endocasts of extinct ischyromyid rodents, the most primitive rodents known from an endocranial record, which provide the opportunity to study the neuroanatomical changes occurring near the base of Sciuridae. The encephalization quotient of C. wilsoni is higher than that of Ischyromys typus from the same epoch, and falls within the range of modern terrestrial squirrel variation, but below the range of extant scansorial, arboreal and gliding sciurids when using cheek-tooth area for the estimation of body mass. In a principal components analysis, the shape of the endocast of C.wilsoni is found to be intermediate between that of primitive fossil taxa and the modern sample. Cedromus wilsoni has a more expanded neocortical surface area, especially the caudal region of the cerebrum, compared with ischyromyid rodents. Furthermore, C. wilsoni had proportionally larger paraflocculi and a more complex cerebellar morphology compared with ischyromyid rodents. These neurological differences may be associated with improvements in vision, although it is worth noting that the size of the parts of the brain most directly involved with vision [the rostral (superior) colliculi and the primary visual cortex] cannot be directly assessed on endocasts. The changes observed could also relate to balance and limb coordination. Ultimately, the available evidence suggests that early squirrels were more agile and visually oriented animals compared with more primitive rodents, which may relate to the process of becoming arboreal. Extant sciurids have an even more expanded neocortical surface area, while exhibiting proportionally smaller paraflocculi, compared with C.wilsoni. This suggests that the neocortex may continue increasing in size in more recent sciurid rodents in relation to other factors than arboreality. Despite the fact that both Primates and Rodentia exhibit neocortical expansion through time, since the adoption of arboreality preceded major increases in the neocortex in Primates, those neurological changes may be related to different ecological factors, underlining the complexity of the inter-relationship between time and ecology in shaping the brain in even closely related clades.

A new early late Oligocene (MP 26) continental vertebrate fauna from Saint-Privat-des-Vieux (Alès Basin, Gard, Southern France)

This fauna results from the short-time excavation of a restricted fossiliferous level, following the opening of a trench for the installation of a gas conduit. Even if the amount of sediment is limited, the diversity of the fauna approaches that of other contemporaneous localities. Among the 40 vertebrate species, a few are amphibious, and most terrestrial. Among them, biochronological markers like Issiodoromys pauffiensis Vianey-Liaud, 1987 (Rodentia, Theridomyidae) are better defined. This species is compared with the type population of the MP 26 Mammalian Paleogene standardlevel (Mas-de-Pauffié, Lot; early Chattian). In addition, evolutionary grades hitherto unknown are described for several less well represented species: a sciurid rodent Comtia n. gen., a molossid bat (Cuvierimops sp.), a probable talpid, and the hyaenodontid Thereutherium thylacodes Filhol, 1876. The familial assignment of the snake Platyspondylia Rage, 1974 is discussed. The locality yielded the possible earliest shinisaurian lizard. The diversity of this new vertebrate fauna is compared to that of several localities from the same biochronological level (mainly Mas-de-Pauffié, Saint-Menoux, Saint-Henri/Saint-André, Mümliswil-Hardberg and Oensingen 11). The choice of Mas-de-pauffié as the reference-locality for MP 26 is therefore supported.

Survival value of suprachiasmatic nuclei (SCN) in four wild sciurid rodents.

Laboratory and field data relevant to the survival value of the suprachiasmatic nuclei (SCN) pacemaker are presented for 4 related North American squirrel species that evolved in habitats with markedly different environmental conditions. Laboratory studies used free-running activity rhythms under constant conditions as the signature of an endogenous pacemaker. Field studies documented the circadian ecology of the 4 species; survival of intact controls was compared, when possible, with an SCN-lesioned group of free-living animals or with wild-caught animals in a laboratory facility that simulated natural conditions. All 4 species were rhythmic in the laboratory as indicated by precise free-running wheel-turning rhythms under constant conditions, as well as by photo-entrainment of free-runs to a 24-hr light-dark schedule. Southern flying squirrels (Glaucomys volans) presumably minimized predation by sleeping in sheltering tree dens during daylight, with awakening by their SCN timer for nocturnal gliding. Eastern chipmunks (Tamias striatus) were strictly diurnal but avoided predation in elaborate dens as well as by facultative hibernation and winter food caches. Antelope squirrels (Ammospermophilus leucurus) were also diurnal with dens for minimizing predation at night. Golden-mantled ground squirrels (Spermophilus lateralis) were diurnal, fossorial species with protective dens; during the extended hibernation in winter, the SCN played a role in limiting the time spent in arousal episodes. Thus, in the evolution of the physiology and behavior of these species, the SCN has become involved in diverse functions ranging from regulation of activity to reduction of energy expenditure during arousal episodes of hibernating ground squirrels.

The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals

Although ultraviolet (UV) sensitivity is widespread among animals it is considered rare in mammals, being restricted to the few species that have a visual pigment maximally sensitive (λmax) below 400 nm. However, even animals without such a pigment will be UV-sensitive if they have ocular media that transmit these wavelengths, as all visual pigments absorb significant amounts of UV if the energy level is sufficient. Although it is known that lenses of diurnal sciurid rodents, tree shrews and primates prevent UV from reaching the retina, the degree of UV transmission by ocular media of most other mammals without a visual pigment with λmax in the UV is unknown. We examined lenses of 38 mammalian species from 25 families in nine orders and observed large diversity in the degree of short-wavelength transmission. All species whose lenses removed short wavelengths had retinae specialized for high spatial resolution and relatively high cone numbers, suggesting that UV removal is primarily linked to increased acuity. Other mammals, however, such as hedgehogs, dogs, cats, ferrets and okapis had lenses transmitting significant amounts of UVA (315–400 nm), suggesting that they will be UV-sensitive even without a specific UV visual pigment.