Elasmosauridae, Vakil & Webb & Cook, 2021
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publication ID |
https://doi.org/ 10.26879/1095 |
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persistent identifier |
https://treatment.plazi.org/id/039687B5-D65E-FFA6-1F14-2A3E4CBEF907 |
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treatment provided by |
Felipe |
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scientific name |
Elasmosauridae |
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Elasmosauridae gen. et sp. indet. (RM FR269)
Figures 6 View FIGURE 6 , 7 View FIGURE 7
Material. Partial postcranial material; 55 vertebrae of which 36 are measurable; most are isolated and free of matrix whereas some dorsals and caudals are cojoined and partially obscured in matrix.
Locality. Near Richmond, Queensland.
Stratigraphic horizon. Toolebuc Formation (upper Albian).
Description. Most centra are complete, but because some centra are partially obscured in matrix, their dimensions were extrapolated by doubling the measurements taken from exposed portions where at least one-half of the centrum was visible. Eleven cervicals have distinct foramina subcentralia ( Figure 6C View FIGURE 6 ) and distinct lateral ridges; some have neural arch bases fused to them with faint suture lines visible, while others show fusion of the zygapophyses (pre- and postzygapophyses) with faint suture lines ( Figure 6A, B View FIGURE 6 ) (CW = 64.4 – 119.5 mm; CL = 50.6 – 93.4 mm; CH = 57.2 – 76.9 mm); 10 dorsals (4 pectorals, 5 dorsals, 2 sacrals) are mostly obscured in matrix but are identifiable on the basis of the position of rib facets; some have neural arches attached to the centra with faint suture lines ( Figure 6D View FIGURE 6 ) (CW = 109.55 – 86.6 mm; CL = 51.5 - 91.55 mm; CH = 59.25 – 78.55 mm); pectorals are distinguishable from dorsals on the basis of their position relative to the cervicals and the position of rib facets borne partly on the centrum and partly on the neural arches; their transition into dorsals is apparent where the rib facets are borne wholly on the neural arches ( Figure 7B View FIGURE 7 ) (CW = 112.35 – 110.9 mm; CL = 80.65 – 81.75 mm; CH = 86.45 – 87.1 mm); two sacral vertebrae are distinguishable from the dorsals and caudals on the basis of the position of rib facets, borne partly on the centrum and partly on the neural arches; the transition from dorsals is apparent since the last six dorsals and the sacral vertebrae are articulated ( Figure 7A View FIGURE 7 ) (CW = 94 mm; CL = 60.95 mm; CH = 65.2 mm); one measurable caudal is identified on the basis of its size and the latero-ventral position of chevron facets, but the remaining 14 identifiable caudals were only partly measured because most are either obscured in matrix or distorted (CW = 84.25 mm; CL = 51.65 mm; CH = 68.2 mm).
Remarks. The original sequence of most vertebrae is lost, but some vertebral sets (especially in the dorsal region) are preserved in articulation. The current sequence is based on the size of vertebrae and gradual change in position of rib facets and is thought to be the original sequence as excavated. Vertebrae have elasmosaurid characteristics (e.g., lateral ridges) (Otero et al., 2017; Sachs and Kear, 2017). Based on the osteological immaturity of the vertebrae, possessing open neurocentral sutures (Brown, 1981), the specimen appears to be a subadult-adult. Specimen RM FR269 was considered potentially referable to Eromangasaurus australis by museum staff based on the similarity in size, morphology, and preservation of the anterior cervicals with those of the E. australis specimen (QM F11050). In the absence of definite shared autapomorphic features, however, this referral should be considered speculative.
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