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Journal of Paleontology 92(4):713–733
modern Taricha in the neural arches and zygapophyses (Naylor 1979), but differ from the proportions of T. oligocenica and Notophthalmus (Naylor, 1978b, 1979). Furthermore, T. lindoei has a similar vertebral length and width to Taricha miocenica described in Tihen (1974), although the neural spine is much higher in the latter (Naylor, 1979; Estes, 1981). The atlas of T. lindoei is robust and slopes anteriorly, and the scapular part of scapulocoracoid is broad, both characters as in extant Taricha and unlike in T. oligocenica (Naylor, 1979; Holman, 2006). The epipleural processes of the pectoral ribs are longer than those of extant Taricha species, as best seen in UOMNH F-59813 (Fig. 6; Naylor, 1979; Estes, 1981; Holman, 2006). As in all members of the genus Taricha, the skull of T. lindoei is broad posteriorly; however, the snout of T. lindoei narrows anteriorly, and the frontosquamosal arch is bony and complete. The premaxilla is fused (Figs. 6, 7). Dermal sculpturing of the skull and frontosquamosal arch is greater than in extant Taricha, but less than in T. oligocenica and Notophthalmus; the overall amount of sculpturing is minor. The preservation of the vomerine tooth row reveals a V-shape, similar to the shape exhibited in T. granulosa.
Materials.—UO 2783 Gray Butte, John Day Formation, Crook County, Oregon: UOMNH F-59813, an imprint/compression of a near complete skeleton and body impression of a young adult, except the distal limbs and girdles (Fig. 6). UO 10744 Fossil locality, John Day Formation, Wheeler County, Oregon: UOMNHF-35553, an impression of a nearly complete skeleton, except for the distal parts of limbs, posterior portion of the tail, most of the ribs, and the pectoral and pelvic girdles; UOMNH F-30616, a partial skeleton impression lacking girdles, distal ends of limbs, and posterior end of tail (Fig. 7.2); UOMNH F-109709, a partial skeleton imprint; UOMNH F-109710, part and counterpart of a flattened partial skeleton; UOMNH F-110577, impression of partial skeleton including skull and several vertebrae (Fig. 7.1); UOMNH F-111395 A–B, flattened partial skeleton in part and counterpart;UOMNHF-37883A–B, part and counterpart of a flattened skeleton, and additional flat- tened partial skull, and a flattened vertebra (Fig. 7.4); JODA 10429 A–B, flattened skull and first several vertebrae com- pressed onto block; JODA 1230, a block with skeletal impres- sions (Fig. 7.3). UCMP John Day Formation locality V5636, Fossil, Wheeler County, Oregon: UCMP 137466, an anterior salamander impression/compression; UCMP 137464, partial skeleton compression.
Remarks.—Naylor (1979) first described Taricha lindoei as the earliest representative of the subgenus Taricha, which at the time contained all extant members of the genus Taricha. The new taxonomy of Dubois and Raffaëlli (2009) has since placed T. rivularis as the lone member of the subgenus Twittya based on iris color, ventral coloration, egg deposition, and habitat (flowing water as opposed to standing or mildly flowing water), while maintaining the earlier caution of Estes (1981) by labeling all Oligocene salamanders assigned to the genus Taricha as Incertae sedis. Estes (1981) stated that T. lindoei may very well represent the earliest member of the subgenus Taricha, but did not find the characterization of multiple subgenera of Taricha in the fossil record to be adequate, given one described individual
each for T. lindoei and T. oligocenica, and fewer than 40 individual skeletal elements in T. miocenica. Without further evidence, it was not possible for Naylor (1979) or Estes (1981) to determine if the combination of smaller size, narrower skull, and absence of sculptured spine tables represented ontogenetic features of one taxon or a taxonomic difference; however, the existence of T. miocenica, which was similar in size to T. lindoei, but possessed less extensive expansion of the spine table than T. oligocenica, was enough for Estes to maintain them as separate species. With the additional specimens now avail- able, we can confirm that even the largest individual assigned to this species (UOMNH F-37883 A–B) bears no dermal cap on the vertebra, as in modern Taricha, while also possessing the broad scapular region of the living group and a narrower rostrum. Additionally, none of the specimens representing this species appears to be larval or juvenile in age; they instead represent young to mature adults. The possibility of T. lindoei and T. oligocenica belonging to the same species and differing in only age at death and preservation is therefore unlikely. The long epipleural rib processes resemble those seen
in T. oligocenica, best seen in (Naylor, 1979). Interestingly, the shape of the vomerine tooth row revealed in T. lindoei bears a V-shape similar to that seen in extant Taricha granulosa. Taricha lindoei consistently presents an anterior narrowing the skull not seen in other members of the genus. It is possible that the body size of T. lindoei is smaller than
T. oligocenica, given that even the most mature specimens do not reach the same size as mature T. oligocenica (Table 2). Notably, the vertebrae of fully adult T. miocenica are also smaller than those of T. oligocenica, and are around the same size as adult T. lindoei (Estes, 1981). The fact that salamandrids are known to be variable in size (Estes, 1981; Duellman and Trueb, 1986; Holman, 2006), combined with the small sample sizes of T. lindoei and T. oligocenica, does not currently permit accurate assessment of these differences, and therefore cannot be used as a diagnostic tool for species identification. Nonetheless, it is worth noting that, while salamanders possess the potential for indeterminate growth, in reality, body size is limited by a number of factors, especially age of first reproduction (Bruce, 2010) and climatic conditions such as temperature and precipitation (Reading, 2007; Caruso et al., 2014). Hence, the difference in stresses between the cooler, drier, seasonal environment preserved in the Big Basin Member versus the wetter, milder environment preserved in the Mehama Formation (due to proximity to the Pacific Coast) may also explain the apparent segregation of species and the difference in body sizes for two fossil newts of similar age.
Phylogenetic analyses
Results.—Because our focus is on the North American newts, specifically the extant genus Taricha and the fossil species attributed to that genus, most of our discussion of these results will focus specifically on the North American taxa. Marjanović and Witzmann (2015) produced a detailed and authoritative discussion of the taxa outside of North America, and with few specimens availabile, we have little to add to their discussion of those taxa beyond a few additional details and an adjustment to
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