The genus Clemmys contains a single living species, Clemmys guttata (Schneider 1792), and an extinct Early Pleistocene species, Clemmys hutchensorumBourque 2016. Today, C. guttata is one of the rarest and most seldom encountered native freshwater turtles in Florida. It is distributed in scattered, discontinuous, and seemingly relictual populations throughout the eastern, north, and central portions of the peninsula (Barnwell et al. 1997; Meylan 2006; Brown et al. 2023). Previously reported fossil records of C. guttata include only a few Late Pleistocene and Holocene accounts from South Carolina and Michigan (Holman 1990, 2001; Bentley and Knight 1993, 1998). Archaeological records are known from Louisiana, Illinois, Michigan, and Wisconsin (Adler 1968; Kozuch 1989; Ernst and Lovich 2009). One of the oldest fossils of C. guttata is from the Ardis Local Fauna (LF) from southeastern South Carolina (Bentley and Knight 1993, 1998). That material consists of a relatively complete shell and isolated postcrania. Radiocarbon dates for the Ardis LF are between 18,940 ± 760 and 18,530 ± 725 years old (Bentley and Knight 1993, 1998).

Florida has a rich Quaternary chelonian fossil record, and most if not all of the state’s native freshwater and terrestrial chelonians can be accounted for in the Late Pleistocene record. However, until the present account, C. guttata was unknown as a fossil in Florida. No confirmed fossils of C. guttata have been reported from Florida (Bentley and Knight 1993; Bourque 2016), and previous reports were confirmed by Bourque (2016) to represent nonankylosed fossils of a large-bodied Terrapene. Meylan (1984) erroneously reported fossil C. guttata from the Late Miocene and Late Pleistocene of Florida, records that were repeated by Hulbert (1992) and Meylan et al. (2001). The oldest fossils of the genus Clemmys are thus of the extinct species Clemmys hutchensorum, which is known from only 4 specimens from the Early Pleistocene Inglis 1C locality in northwestern peninsular Florida (Bourque 2016). Here we describe the first fossils of the living species C. guttata in Florida and discuss the significance of their provenience in the state and the southeastern United States.

LOCALITY BACKGROUND

The Wacissa River is located approximately 30.6 km southeast of Tallahassee, Florida. It originates in central Jefferson County, Florida, near the toe of a marine erosional escarpment called the Cody Escarpment and flows southward for approximately 20 km across the Woodville Karst Plain Province before it joins the Aucilla River just north of the US 98 Bridge. Baseflow is from at least 12 artesian springs that discharge along the upper mile of the river (Scott et al. 2004). The Wacissa River is relatively shallow and does not occupy a well-developed channel because limestone and dolostone bedrock are at or very near the surface. Where the river encounters bedrock, it branches out into numerous smaller rapidly migrating channels.

Strata exposed in the Wacissa River include freshwater shell marl deposits, quartz sand lenses, and peat that overlie the Oligocene Suwannee Limestone (Balsillie et al. 2006). Fossil vertebrate remains are commonly found in the bed load mixed with the remains of modern taxa and material eroded from adjacent bank deposits. As a result, it is difficult to ascertain the age or the stratigraphic context of fossil material recovered from the bottom of the river. However, the authors have observed vertebrate faunal remains in the Wacissa River that appear to be in stratigraphic context. Additional investigations are needed to address the age and stratigraphic context of the Clemmys guttata fossils described here.

Clemmys guttata fossils presented here are from the lower portion of the Wacissa River, in Jefferson County, Florida (Fig. 1). All are well-permineralized similar to Late Pleistocene fossils from this river system. All fossils collected along the Wacissa represent either still extant taxa or Late Pleistocene index taxa including the giant pampathere armadillo Holmesina septentrionalis, as opposed to Holmesina floridanus, which is present in Early Pleistocene deposits (Hulbert and Morgan 1993). Fossils previously collected over many years from Wacissa localities 1–3 are Late Pleistocene, including taxa such as Bison antiquus. We have not seen any evidence that the paleofaunas along the Wacissa River discussed here are older than Late Pleistocene (Rancholabrean) in age.

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Three sublocalities (JE005, JE008, and JE009) in relatively close proximity to one another contain Clemmys guttata fossils. More specific locality information for these localities is available on file at the Division of Vertebrate Paleontology, Florida Museum of Natural History. All sublocalities contain a sandy brown peat layer from which the fossils eroded.

METHODS

SYSTEMATIC PALEONTOLOGY

Order TESTUDINES Batsch 1788

Family EMYDIDAE Rafinesque 1815

Subfamily EMYDINAE Rafinesque 1815

Genus CLEMMYSRitgen 1828

CLEMMYS GUTTATA (Schneider 1792)

(Fig. 2)

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Referred Material. —

Three complete nuchals, UF 557132–UF 557134 (Fig. 2 A–F).

Locality. —

Lower Wacissa River Basin, Jefferson County, Florida. Sublocalities: JE005 (UF 557132), JE008 (UF 557134), JE009 (UF 557133).

Age. —

Late Quaternary; Late Pleistocene, Rancholabrean NALMA, and/or Holocene.

Remarks. —

Only fossil nuchals of C. guttata have been recovered from the Wacissa River Basin. Unfortunately, the nuchal region of the extinct Early Pleistocene species Clemmys hutchensorum is currently unknown so comparisons between these 2 species cannot be made at this time. The Wacissa nuchals are assigned to the species C. guttata based on their Late Pleistocene–Holocene age, provenience within the range of living C. guttata, and their being indistinguishable from extant adult C. guttata (Table 1, Fig. 3).

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Table 1. Selected nuchal measurements of fossil and Recent Clemmys guttata. L, total nuchal length; W, total nuchal width; AW, anterior margin width (measured at anterior-most M1 suture of the nuchal); V1W, vertebral 1 width (inter V1-PL1 sulcus width measured at the anterior-most widest point of V1 visible on the nuchal face); DCL, dorsal cervical scute length; VCL, ventral cervical scute length. All measurements in mm.

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DESCRIPTION

All 3 nuchals from the Wacissa River Basin are identified as C. guttata by a unique combination of the following: relatively small adult size; smooth dorsal surface that lacks carination, ornamentation, or distinct well-incised growth annuli; V1 broad with lateral sulci situated on the distal most ends of nuchal and/or C1 only; cervical notch small to absent; cervical scute long and narrow dorsally and broader ventrally with long underlap; M1 with long underlap and pronounced step at visceral transition.

UF 557132–UF 557134 are small in size and consistent with full-grown adults of C. guttata (Table 1 and Fig. 3). They are relatively smooth in texture except for some faint growth annuli that are most pronounced at the anteriormost V1 and ventral M1 sulcus at the visceral transition. In all of the nuchals, the cervical scute is long and narrow dorsally and wider ventrally, and the anterior cervical-M1 margin is relatively straight transversely with only a very slight cervical notch. There is a distinct pronounced step at the M1 to visceral transition, where M1 is at its thickest. This step and M1 swelling are seen in the emydines Clemmys, Glyptemys, and Actinemys, but absent in Terrapene, the only sympatric emydine in the Wacissa Fauna. The nuchal to N1 suture indicates broad contact with N1. The width of V1 is variable among the 3 nuchals and all fall within the range of variability observed in extant C. guttata. In UF 557134 (Fig. 3A–B) the anterior termini of the V1-PL1 sulci are wholly contained on the dorsal face of the nuchal. In UF 557133 (Fig. 3E–F) the V1-PL1 sulci barely overlap the nuchal at its widest point and would have overlapped onto and terminated on P1 in life. In UF 557132 (Fig. 3C–D) the V1-PL1 sulci are asymmetrical, on the left there is no V1-PL1 overlap onto the nuchal, and on the right there is minimal overlap at the widest point.

DISCUSSION

Clemmys guttata is one of the most infrequently encountered turtles in Florida with disjunct isolated populations (Meylan 2006; Krysko et al. 2019). It is similarly rare in the fossil record. Despite thousands of catalogued and still uncatalogued Middle-Late Cenozoic fossil turtle specimens housed in the FLMNH collection, no fossils of C. guttata have been previously discovered in Florida. Their rarity in both the fossil and Recent record suggests that C. guttata arrived in Florida late in geologic time (e.g., Late Pleistocene to Holocene), which is corroborated by the age of the Wacissa fossils. The Wacissa fossils additionally provide evidence against previous hypotheses that the isolated populations of C. guttata in Florida today are the result of pet releases and/or escaped captives (Neill 1954; Ernst 1972; Ashton and Ashton 1985; Hipes et al. 2000), rather than relictual (Barnwell et al. 1997; Meylan 2006). Meylan (2006) reasoned that extant C. guttata populations in Florida are natural in large part due to the remoteness of multiple populations. The fossils confirm that C. guttata occurs naturally in Florida and represent a regional paleopopulation rather than a Recent human introduction. However, one cannot completely discount the possibility that the presence of C. guttata in Florida today could be due in part to some introduction by Florida’s indigenous and/or prehistoric peoples. Remains of C. guttata recovered at an archaeological site in Louisiana, well outside of the current geographic range in the southern United States, demonstrates that C. guttata was utilized and transported by indigenous peoples (Kozuch 1989). RM and GHM frequently encounter human artifacts in areas of the Wacissa River where C. guttata fossils were collected, and the nearby Ryan-Harley archaeological site has a rare Suwannee lithic assemblage in association with extinct and extirpated Late Pleistocene taxa, such as the tapir Tapirus veroensis, camelid Paleollama mirifica, and giant tortoise Caudochelys cf. C. crassiscutata (Dunbar et al. 2006; Smith 2020). Currently no evidence indicates the C. guttata fossils are the result of anthropogenic introduction or refuse, and as such, the fossils more confidently represent a natural occurrence of the species.

Clemmys guttata is rare in the Florida Panhandle, with few vouchers along the Gulf Coast (Krysko et al. 2019). This is the first documented record of the species, fossil or living, from the Wacissa River and Aucilla River Drainage as a whole. Meylan (2006) includes a map (Fig. 15-3) that indicates a record in the northern reaches of the Aucilla Basin; however, the point is a misplaced location that should have appeared 5 miles south of Jasper in Hamilton County, Florida (P. Meylan, pers. comm.). Multiple vouchers exist just to the west of the Wacissa River from the lower Apalachee Bay–St. Marks Drainage, mostly within the St. Marks National Wildlife Refuge (Barnwell et al. 1997; Meylan 2006).

Clemmys guttata prefers wetland mosaics that include both temporary and permanent aquatic habitats such as shallow soft-bottomed wetlands associated with clear streams (Ernst and Lovich 2009; pers. observ.). Habitats include swamps (often with Sphagnum moss), ephemeral ponds, bogs, fens, wet meadows, marshes, and brackish streams, among others (Ernst and Lovich 2009). They are often abundant in coastal brackish habitats, as is the case for the St. Marks River population just west of the Wacissa (Meylan 2006; Krysko et al. 2019). It is possible that the portion of the lower Wacissa with C. guttata fossils was more brackish than today at the time of fossil deposition, with Late Pleistocene shifts in sea level or during the Early Holocene Sea Level Rise (Randazzo and Jones 1997; Smith 2020). This scenario is further supported by the co-occurrence of cheloniid sea turtles, Malaclemys terrapin, and freshwater turtle fossils from the Wacissa. With these habitat preferences in mind, it is not surprising that the 3 fossil nuchals discussed here come from peat deposits, which likely formed in more lentic water bodies than the lotic main body of the Wacissa. The peat likely formed in smaller streambeds or peripheral backwaters of the main Wacissa River body, which eventually cut through these deposits as the hydrology, position, and flow rate changed over time. Peat deposits from the Wacissa Canal were more deeply exposed due to human enhancement of that waterway, which undoubtedly cut through more lentic strata from which the C. guttata fossils eroded out of.

The oldest fossils of the genus Clemmys are from the Gulf and Atlantic Coastal Plains of the United States (Bentley and Knight 1993, 1998; Bourque 2016). Likewise, the Atlantic Coastal Plain is the provenience of the oldest fossils of the similar-sized and somewhat closely related bog turtle, Glyptemys muhlenbergii, from the Irvingtonian of Maryland (Holman 1977, 1995). The Wacissa records of C. guttata add to the accounts of Clemmys from the Gulf Coastal Plain of Florida during much of the span of the Pleistocene to the Holocene, with Clemmys hutchensorum from the Early Pleistocene, latest Blancan (Bourque 2016), and C. guttata from the Latest Pleistocene–Holocene. The Wacissa and Ardis fossils demonstrate that C. guttata was well distributed in the Gulf-Atlantic Coastal Plain by the Late Pleistocene, which supports this region as a plausible place of origin for the species. However, this region notably has more known Neogene vertebrate fossil-bearing deposits than northern and inland regions of the eastern United States (Tedford et al. 2004). The absolute age of the C. guttata fossils from the Wacissa River requires further investigation to conclude how they compare in age to the Ardis Local Fauna specimens of southeastern South Carolina. As such, the confirmed oldest fossils of C. guttata are from Ardis at 18,940 ± 760 and 18,530 ± 725 years old (Bentley and Knight 1993, 1998).