Museum specimens serve as the bedrock of systematic and taxonomic research and provide the basis for repeatability or reinterpretation of preserved aspects of phenotypes. Specimens are also fundamental to fields such as ecology, behavior, and development. Each specimen is a record of biodiversity and documents a particular species present at a particular place at a particular time. As such, specimens can provide key evidence for biodiversity and conservation initiatives. Four aspects of natural history collections and their use are discussed here: 1) collection, curation, and use of specimens, particularly non-traditional specimens; 2) the use of specimens and technological advances in morphology, ontogeny, systematics, and taxonomy; 3) specimen use in other fields of biology and ecology; and 4) specimen use in education and outreach. Collections, and their vitality, depend on both their continued roles in traditionally supported fields (e.g., taxonomy) as well as emerging arenas (e.g., epidemiology). Just as a library that ceases buying books becomes obsolete, or at least has diminished relevance, a natural history collection that does not continue to grow by adding new specimens ultimately will limit its utility. We discuss these roles of specimens and speak directly to the need to increase the visibility of the inherent value of natural history collections and the care of the specimens they protect for future generations.

Museums provide a wealth of scientific information via preserved natural history specimens, including but not limited to dietary, morphological, and geographic distributions of organisms. In the modern molecular age, however, fluid-preserved museum collections have not always been at the frontline for generating useable data, despite the fact that for some species, only museum specimens are known, with no fresh genetic materials available. We are now at a major shift in our ability to use museum specimens for molecular phylogenetics, where modern subgenomic sequencing techniques better allow for successfully sequencing hundreds to thousands of phylogenetically informative loci for historical specimens, including formalin- and fluid-preserved amphibians and reptiles. Here, I review the current state of the field, with respect to studies which have successfully generated high-throughput molecular datasets using fluid-preserved specimens for herpetofauna, particularly for systematic studies. Although only six publications fitting the search criteria were found, these studies provide a wealth of knowledge on the uses of museum herpetological specimens for modern work and illustrate just how important historical specimens are for enhancing our current understanding of species genetic structure, phylogenetic placements, and for disentangling taxonomic conundrums. In an age where both museums and general collecting come under critique from the general public, this review emphasizes the continued importance of museum specimens across all subfields in the study of amphibians and reptiles.

The University of Washington Fish Collection is a state-funded collection shared between the University of Washington School of Aquatic and Fishery Sciences and the Burke Museum of Natural History and Culture dating back to 1919. Early collecting followed the interests of curators and university class field trips, with a slow and steady growth rate up until the late 1970s. At that time, recognizing that state and federal agencies routinely collect specimens as part of their fishery and resource management efforts, we sought out partnerships with several local agencies, most notably the National Oceanographic and Atmospheric Administration Fisheries Department, to provide collections support for the natural history specimens collected through their survey work. The millions of specimens collected through these efforts, including adults, juveniles, eggs, larvae, skeletal materials, otoliths, and tissue samples, along with detailed locality data, are now freely available to researchers around the world. Vouchering specimens adds value to agency research by allowing for verification of results of work critical to the management of our resources, including supporting forensic vouchering for law enforcement. Our collection benefits not only from the huge number and diversity of specimens we can make available to researchers, but also through training opportunities for our students who help to curate the collections and often participate in survey fieldwork along with agency scientists. I outline these partnerships and the benefits to both parties as we curate these vast specialized collections.

For generations, organismal biologists have learned their craft in hands-on laboratories that teach anatomy, evolution, natural history, systematics, and functional morphology through specimen collection, observation, comparison, and manipulation. Though these activities teach the comparative method that lies at the heart of our discipline, students without access to specimen collections have been excluded from this foundational experience. To fill that gap, we developed a virtual collection of photographs and 3D specimen models and designed entirely online versions of courses in ichthyology and systematics of fishes. The virtualization allows students to illustrate and compare specimens in online labs, identify species from different habitats using dichotomous keys, contextualize the relationships of species, recognize synapomorphies using a phylogeny, take online specimen-based practical exams, and help each other recognize adaptations and diagnostic features on threaded discussion boards. The classes built around the collection educate and provide university credit to students lacking access to similar courses, and their infrastructure allowed face-to-face instruction to shift online rapidly after 2020's novel coronavirus shut down our brick-and-mortar campus. While we may never be able to replicate the aroma of oil-laden alcohol online, specimen virtualization opens access to experiential learning to an underserved and widespread audience; allows new generations of students to develop crucial skills in observation, comparison, and inference; and affords substantial instructional resiliency when unexpected challenges arise.

Urbanization is a major contributor to habitat loss and fragmentation and is considered a global threat to biodiversity. We studied reptile and amphibian species diversity and abundance in a highly fragmented landscape adjacent to the second largest metropolitan area in the United States. Habitat patches in our study area were made up of remnant native vegetation surrounded by roads, housing, and other urban development. Species richness and diversity were positively associated with patch size, but patch age was not significantly associated with community characteristics. Four relatively common species were not detected in the small patches, indicating the possibility they had been extirpated by the time monitoring began, and six rarer species were not detected or detected only once in these patches. Although the patch size effect on species diversity was strong, we found that several of the small habitat patches had similar diversity to large patches, indicating potential value of these small habitat patches in protecting species as “microreserves.” In addition, one lizard species was found to be significantly more abundant in the smaller patches. To determine if abundance changed over time, we compared capture rates for four common lizards at the same sites ten years later. For three of the four species, abundance decreased over that period, specifically in the small patches. Although our long-term monitoring has confirmed that the full suite of herpetofauna is currently preserved in the study area overall, declines even in the common species over time hint at the potential severity of the threat of urbanization to rare species.

The vertebrate stress response involves the release of adrenal hormones which make stored energy available to respond to stressors. The ability to effectively mobilize and distribute glucose is an important component of successful stress coping mechanisms. While many studies of reptiles have examined the hormonal response to stress under diverse contexts, comparatively few studies have focused on the glycemic response. Here we analyze the glycemic response to short-term capture stress in two species of snake, the Northern Water Snake (Nerodia sipedon) and the Pygmy Rattlesnake (Sistrurus miliarius), across reproductive contexts using a FreeStyle Lite (FSL) glucometer. The FSL is a point-of-care glucometer that provides a fast, inexpensive, and efficient method to monitor glucose concentrations in human whole blood. However, despite increasing use in reptiles, no studies have thoroughly validated their use in snakes or other squamates. We used a traditional colorimetric glucose assay to validate results using the FSL on both fresh whole blood and stored plasma. Hyperglycemia was induced by short-term capture stress in both species. The hyperglycemic response did not vary by sex, reproductive condition, or energetic status (body condition index, BCI). However, baseline and stress-induced glucose was higher in male compared to non-reproductive female N. sipedon. In S. miliarius, the magnitude of the glycemic response was positively correlated with cloacal body temperature. Baseline glucose was below the limit of detection in many individuals of both species, which may limit the utility of the FSL and other handheld glucometers in studies that seek to describe baseline values. Glucose estimates were strongly correlated when comparing all methods, indicating that the FreeStyle Lite is a potentially valuable tool to effectively compare the glycemic response to experimental treatment or to track changes in the glycemic response of snakes over time. However, significant bias was observed when comparing the three methodologies, suggesting that caution should be used when comparing results from the FSL and other point-of-care glucometers to reference intervals generated using other methodologies.

Gymnophion amphibians (caecilians) are less well studied than the other two orders of extant amphibians: Anura and Caudata. We describe the first recorded presence of supernumerary (B) chromosomes in the order Gymnophiona, where a lone intensely stained B chromosome was observed in the somatic metaphase and meiotic complements of the Indian ichthyophiid, Uraeotyphlus gansi. Given the rarity of B chromosomes in caecilians and their sporadic presence within U. gansi, it is likely that these represent aneuploidy and are a recent acquisition derived from centromeric drive.

Parotocinclus kwarup, new species, is described as a new hypoptopomatine cascudinho from tributaries of the upper Xingu River in the Amazon basin of Brazil. The new species is distinguished from its congeners in northeastern and southeastern Brazil by having the cheek canal plate elongated posteriorly on the ventral surface of the head and in contact with the cleithrum. Parotocinclus kwarup, new species, is diagnosed from other species of Parotocinclus in the Amazon, Orinoco, and Guianas watersheds by the number of oral teeth, the snout length, having odontodes on the ventral surface of the first pelvic-fin ray bent and pointing mesially, lacking a Y-shaped light marking dorsally on the head (from the posterodorsal margin of orbit to posterior parieto-supraoccipital tip), lacking premaxillary and dentary accessory teeth, and having an adipose fin. The extinction risk of the new species is preliminarily assessed as Least Concern based on its wide distribution area and its inferred presence in the large Xingu Indigenous Park.

Three new species of small snailfishes, with maximum lengths up to only 60 mm, are described from collections in the Aleutian Islands taken during fisheries resource assessment surveys conducted by the U.S. National Marine Fisheries Service. Previous molecular analyses demonstrated that two of the species are closely related; the third species was found among material thought to consist only of one of these two species. Two of the new species are distinguished from all other species of Careproctus on the basis of an anterior dorsal-fin lobe with exserted rays and bodies with widespread small rounded bumps covered with tiny prickles. They are distinguished from each other on the basis of fin ray and vertebral counts, as well as differences in body shape. The third new species is diagnosed from all other species of Careproctus by having a small teardrop-shaped body, with loose thin skin and without an anterior dorsal-fin lobe, as well as by high counts of meristic characters, especially pectoral-fin rays. Each species is found widely within the Aleutian Islands from west of Kiska Island in the west to north of Umnak Island in the east at depths of 90 to 447 m.

Despite the increasing number of studies on the systematics of the Stephanoberycoidei (bigscales, pricklefishes, gibberfishes, hispidoberycids, and whalefishes) globally, knowledge about the diversity and distribution of the group in the western South Atlantic still remains fragmentary. In this study, we present new anatomical (meristic and morphometric) and distributional data for 18 species of the Stephanoberycoidei based on the examination of 150 specimens recently collected during the ABRACOS (Acoustics along the BRAzilian COaSt) expeditions off northeastern Brazil, including the Rocas Atoll, Fernando de Noronha Archipelago, and the seamounts off Rio Grande do Norte State, and additional museum specimens. In the Melamphaidae, remarks on the taxonomy of Melamphaes polylepis and of the Poromitra crassiceps and P. megalops species groups are made based on specimens examined. In addition, Scopeloberyx opercularis, currently considered as a junior synonym of Scopeloberyx robustus, is recognized as a valid species. Among the species identified, nine have their distributions extended in the western South Atlantic based on confirmed records: Melamphaes polylepis, M. typhlops, Poromitra megalops, Poromitra sp., Scopeloberyx opercularis, Scopeloberyx opisthopterus, Scopelogadus mizolepis, Cetostoma regani, and Rondeletia loricata. Eight further species are reported for the first time in Brazilian waters: Cetomimus sp. 1, Cetomimus sp. 2, Ditropichthys storeri, Gyrinomimus bruuni, Melamphaes eulepis, M. leprus, M. longivelis, and Melamphaes sp. Additional remarks on the taxonomy and distribution of the Stephanoberycoidei in the western South Atlantic are also provided.

The skeletal features of six species of salamanders in the genus Bolitoglossa (subgenus: Magnadigita) were described and compared. Many osteological features of the Magnadigita subgenus were found to be highly conserved, such as the presence of bifurcated first caudal vertebrae and distal expansions on the terminal phalanges. Key traits were identified that were distinct among the species in this study, including the prefrontals and frontoparietal fenestrae; we suggest these traits may be useful in future taxonomic studies of Bolitoglossa. We also discuss the evolution of paedomorphosis and webbed feet in relation to Magnadigita. Bolitoglossa diaphora has highly webbed feet but lacks the osteological features typically associated with this paedomorphic trait, such as fused or accentuated elements, but rather has the osteological features typical of other Magnadigita.

Invasive fishes continue to adversely impact the structure and function of aquatic ecosystems globally. The effects of introduced populations may, however, differ according to key characteristics such as size, abundance, invaded habitat type, and community composition. Here, we conduct diet analyses to describe the feeding characteristics of the nonnative North American Pumpkinseed, Lepomis gibbosus, across multiple habitat types (three lentic and three lotic systems) and fish size classes. Pumpkinseeds exhibited a broad diet, inclusive of numerous threatened species groups (e.g., amphibians) and commonly included dipterans and detritus overall. Observed diets were more diverse in ponds compared to stream habitats, as well as for larger individuals, with individuals in streams tending to consume terrestrial insects in higher numbers. Our results show that the impact of Lepomis gibbosus differs not only according to size and ontogeny, but also depending on the habitat type, probably due to different prey availabilities and biotic interactions. This has implications for ecological impacts of this invasive species in lentic and lotic systems, with a generalist diet potentially facilitating impacts on a broad range of prey taxa, with concomitant adverse competitive effects on native predator species.

Understanding thermal and moisture regimes in nesting habitat is an important step in management and restoration of at-risk turtle habitat because anthropogenic stressors that affect these key properties impact hatch success. In rock barrens landscapes, freshwater turtles are known to nest in unique shallow-soil deposits in depressions in the bedrock. Our objective was to provide the first comprehensive multi-scale assessment of turtle nesting habitat in a rock barrens landscape. At the nest-site scale, we characterized nesting habitat, tested for evidence of nest-site selection by the Blanding's Turtle (Emydoidea blandingii), Spotted Turtle (Clemmys guttata), and Midland Painted Turtle (Chrysemys picta marginata), and examined the effects of nest temperature and moisture on egg hatching success. At the landscape-scale, we conducted a systematic survey across 660 ha to assess the availability of nesting habitat. Although rock barrens were the second most dominant land cover type, the availability of suitable nesting habitat with deeper soil and an open canopy was limited to 11% of the rocky outcrops and <3% of the study area. We found that shallow rock barrens nesting habitat had unique soil temperature and moisture dynamics that were linked to soil properties and bedrock morphology to provide successful incubation conditions. In particular, mean daily temperature, variance of soil saturation during incubation, and their interaction had a significant effect on egg hatching success, regardless of egg mass. There was also evidence that turtles selected sites that were warmer and drained faster than paired haphazard sites despite having other similar characteristics. Given that the loss and degradation of nesting habitat is of conservation concern for the survival and recovery of at-risk turtle species, we recommend that key management strategies should include stronger protection of critical rock barrens nesting habitat and the development of landscape-appropriate strategies for restoration and creation of nesting habitat.

The Scinax catharinae clade comprises the S. perpusillus and S. catharinae groups. The S. catharinae group has 38 species, mostly from Brazil's Atlantic Forest. We describe a new species of S. catharinae group based on external morphology, color pattern, and bioacoustics. The new species calls from herbaceous vegetation of slow-flowing streams from Santa Teresa, State of Espírito Santo, southeastern Brazil. The new species is distinguished from species of the S. catharinae group by the following combination of characters: male SVL 24.8–28.3 mm and female SVL 31.2–38.6 mm; males with hypertrophied forearms and inguinal glands; interocular region with a dark blotch not exceeding beyond the anterior margin of tympanic level; black blotches on a whitish-green background on the inguinal region and hidden surfaces of legs; call type A of 0.301–0.883 s, and 12–30 notes emitted at a rate of 31.4–42.0 notes/s. We also provide remarks on its natural history and conservation status.

For amphibians that oviposit in temporary aquatic systems, there is a high risk of desiccation-induced offspring mortality when water evaporates prior to the completion of embryo or tadpole development. Such a strong selective pressure has led to the evolution of a variety of traits in reproducing females and their offspring to improve the odds of reproductive success when free-standing water is temporarily available. Herein, we describe an adaptive function of froth nesting in the Sandpaper Frog, Lechriodus fletcheri, as a possible maternal strategy for protecting embryos from the immediate risk of desiccating in highly ephemeral pools that frequently dry prior to hatching. Field observations revealed that embryos located near the core of nests remained alive and continued to develop for several days after becoming stranded out of water due to declining water levels, with embryo viability maintained long enough for additional rainfall to recharge pools and support hatching of tadpoles into water in some cases. In laboratory trials, the proportion of embryos surviving in nests exposed to desiccating conditions was positively correlated with nest volume, while the rate of water loss relative to nest mass declined, both of which are likely a function of reduced surface area relative to volume in larger nests. We suggest that the encapsulation of embryos within an aerated mucus shields them from desiccation by trapping moisture around their external surfaces. As embryos of L. fletcheri complete development rapidly, the ability for the froth nest to protect against desiccation for several days may allow embryogenesis to be completed largely out of water despite the larval phase not being terrestrial. These results suggest froth nesting has played an important role in facilitating this species' use of ephemeral habitats that most other amphibians with aquatic reproductive modes are incapable of exploiting.

The 2011 nuclear accident in Fukushima, Japan was one of the largest anthropogenic releases of radioactive contamination in history, and many questions remain regarding its ecological impacts. As part of a larger study estimating animal movements and radiation exposure within the impacted area, we used a combination of VHF and GPS transmitters to estimate home range size and habitat use of nine Japanese rat snakes (Elaphe climacophora and E. quadrivirgata) over three months within the Fukushima Exclusion Zone. Short-term a-LoCoH ranges varied from 0.15–6.80 ha, and daily movements ranged from 30–116 m. Short-term home ranges included more areas close to streams, buildings, and roads, as well as more grassland and less evergreen forest than expected given the availability of these habitat components on the landscape. Within their home ranges, snakes selected areas close to streams and avoided evergreen broadleaf forests. They also frequently used habitat features such as trees and buildings, although use of buildings was highly variable among individuals. The limited distance snakes moved compared to more mobile species suggests snakes could be useful bioindicators of local contamination. However, radionuclide exposure will still vary considerably among individual snakes within localized areas due to differences in habitat use.

A new species of Loricariichthys is described from the Rio Itabapoana and Rio Itapemirim basins, two small, adjacent, yet independent, coastal drainages in south Espírito Santo State. Loricariichthys melanurus, new species, is distinguished from most congeners by the anterior margin of abdominal plates falling at or slightly ahead of the transverse line between the pectoral-fin spines, not reaching the level of the lower end of the gill slits, further on other features of external morphology. The new species can be differentiated from L. castaneus, the most similar and geographically closest species, by the possession of a conspicuous black marginal band at the distal portion of middle and lower caudal-fin rays and a darkened distal half of dorsal fin, which are absent in the former. Samples analyzed of the two species have a COI pairwise genetic distance of 4.6%. The paleodrainage reconstruction inferred for a sea-level-retreat of maximum glacial period of the Pleistocene suggests that neither the Itabapoana and Itapemirim Rivers, nor the other coastal rivers of eastern Brazil, where L. castaneus occurs, have been in contact during this period.

A new and previously cryptic fish species, Polymixia hollisterae, new species, proposed common name “Bermuda Beardfish,” is described from two voucher specimens collected in 1997 at a depth of about 280 fm or 512 m on the NW slope of the Bermuda Platform, and a third voucher collected by a midwater trawl in the north-central Gulf of Mexico. The species belongs to the paracanthopterygian acanthomorph genus Polymixia, family Polymixiidae, order Polymixiiformes, and is named after pioneering ichthyologist, ocean explorer, and conservationist Gloria E. Hollister (Anable). It is distinguished from all other species in the genus by its greater dorsal and anal fin heights (19% and 14% of SL, respectively), its extremely long pectoral and pelvic fins (22% and 14% of SL, respectively), its relatively large eye diameter (34% of total head length), and its morphologically distinctive first anal-fin radial. It has a unique pigmentation pattern on the dorsal, anal, and caudal fins consisting of narrow, dark black patches near the tips of the longest few soft dorsal- and anal-fin rays, and a caudal-fin margin with a dark black fringe covering the distal fourth of the fin. Based on an earlier molecular study that revealed it to be a cryptic species, P. hollisterae, new species, is closely related to P. japonica, but it differs by 20–33 nucleotides in a total alignment of 4,983 nuclear and mitochondrial sites. The new species shares a distinctive scale morphology with P. japonica and P. nobilis (the type species); an intermediate number of dorsal-fin rays (V,31–32), like P. japonica (V,31–34); a distinctive preopercle shape with P. japonica, P. lowei, and P. berndti; and a low number of pyloric caeca with P. lowei and P. berndti. Pored lateral-line scales number 35, an intermediate number compared to reported counts of other species (31–39). The three supraneurals are sigmoid-shaped like those of P. nobilis, while dorsal-fin proximal radials interfinger with neural spines in a unique pattern. Body shape, as studied with measurement proportions and multivariate morphometrics, is distinguished by a relatively large head, large eyes, long jaws, and a more streamlined pre-dorsal body profile than its congeners. Further research and additional collecting will be needed to ascertain the geographic distribution and conservation status of the new species.

The Rio Grande Cichlid, Herichthys cyanoguttatus, is native to northeastern Mexico and southern Texas and has been introduced at many places in the US. Recent research has indicated that the true identity of at least some populations of Herichthys cf. cyanoguttatus in Louisiana is H. carpintis and not H. cyanoguttatus. In both their native and introduced ranges, H. carpintis seems to occupy a more lowland/coastal distribution than does Herichthys cyanoguttatus, suggesting that the two species may differ physiologically or ecologically in their ability to invade new environments. Previous research has found that Herichthys cf. cyanoguttatus from Louisiana (which were most likely H. carpintis) have a high tolerance to salinity and pose a threat to both fresh and brackish waters, but the osmoregulatory capacity of H. cyanoguttatus from Texas is unknown. To determine if H. cyanoguttatus from Texas might also have a high tolerance to salinity and pose a threat to both fresh and brackish waters, we performed three experiments to assess response to salinity challenges in H. cyanoguttatus from Texas and in H. carpintis from Louisiana. In response to acute moderate salinity challenge, we found a non-significant salinity*species interaction in change in body mass, a species difference in hematocrit, and no differences in plasma chloride or osmolality. In a 120-day chronic salinity exposure, salinity concentration was inversely related to growth rate, but there was no difference in growth between the two species. In an acute challenge, high salinity concentrations had a strong negative effect on survival, but survival was not different between the two species. Both species were highly tolerant of salinity, indicating that both species might be able to use brackish waters in coastal areas to expand their ranges in the US. Finally, we found that H. cyanoguttatus from Texas spent more time swimming than did H. carpintis from Louisiana, suggesting that the two species could differ in the way they interact behaviorally with native fish communities.

Thermal ecology and microhabitat use by lizards are affected directly and indirectly by intrinsic (e.g., sex and body size) and extrinsic (e.g., environmental seasonality, vegetation cover, and wind speed) factors. Herein we evaluate the effect of seasonality and sex on field thermal ecology and microhabitat utilization of a population of Anolis carlliebi inhabiting a xeric scrubland in Central Mexico. Lizards were found primarily in full and filtered sun conditions, strongly associated, respectively, with inflorescences and leaves of Agave stricta. Males were slightly larger than females. Mean field body temperature did not differ between sexes within seasons, but males used higher perches than females in the warm season. We observed a seasonal shift in body temperature and perch use in males, which exhibited higher body temperatures and occupied wider and higher perches in the warm season. Female body temperature and perch use did not differ between seasons. This study reports the first case of a population of Anolis specializing in a species of Agave as microhabitat. These results add to our understanding of thermoregulation and microhabitat use of mainland species of Anolis since they face different environmental pressures than Caribbean species.

Neotropical suckermouth armored catfishes (Loricariidae) are known to exhibit terrestrial behaviors, but these have been poorly described. The goals of this study are to describe (1) the terrestrial locomotion of loricariid catfishes, (2) how their unique morphology may affect terrestrial movements, and (3) how behavior, performance, and kinematics relate to species and endurance. The terrestrial locomotion of four loricariid species (three species of Pterygoplichthys and one species of Hypostomus) was recorded using high-speed cameras. Videos were digitized in MATLAB and ImageJ to compare performance and kinematics between species and over time. Morphology was described using micro-computed tomography scans and dissections. Loricariid catfishes use a novel, highly asymmetric form of axial-appendage-based terrestrial locomotion involving their mouth, pectoral fins, pelvic fins, posterior axial body, and tail. As this behavior is so unlike any other described locomotor behavior, we have created a new word to describe it: reffling. These species have numerous unique morphological traits that may greatly reduce body and fin flexibility. Because loricariids are so inflexible, they may be constrained into reffling as their only means of terrestrial locomotion, but their stiffness may improve force transmission, allowing them to be among the fastest fishes on land. Overall, all four species examined had very similar terrestrial kinematics and performance. Their performance generally declined over time, but different species had different endurance levels. Because many loricariid species are invasive throughout the world, it is important to consider their capacity to disperse into new bodies of water overland in management plans and risk assessments.

Phylogenetic relationships among the four currently recognized species in the genus Erimyzon were reconstructed using sequence data obtained from the mitochondrially encoded COI and the nuclear-encoded IRBP2 genes. Maximum likelihood and Bayesian analyses yielded five groups of Erimyzon. Three of the clades corresponded to the species E. oblongus, E. tenuis, and E. claviformis. Individuals identified as E. sucetta were split into two separate clades, with one clade more closely related to E. oblongus than to the other E. sucetta clade in three of four analyses. Two instances of putative hybridization between sympatrically distributed species were also detected, one involving E. oblongus and E. sucetta and the other involving E. claviformis and E. tenuis. The results suggest that the currently recognized E. sucetta comprises two species, with potentially non-overlapping distributions. Further morphological investigation is warranted to provide additional support for recognizing this putative fifth species of Erimyzon.