A comparative atlas of selected skeletal elements of European urodeles (Amphibia: Urodela) for palaeontological investigations Author Macaluso, Loredana Author Wencker, Lukardis C M Author Castrovilli, Maria Author Carnevale, Giorgio Author Delfino, Massimo text Zoological Journal of the Linnean Society 2023 2023-03-01 197 3 569 619 https://academic.oup.com/zoolinnean/article/197/3/569/6693955 journal article 10.1093/zoolinnean/zlac063 0024-4082 7690954 IDENTIFICATION KEY Otic–occipitum complex 1. Smooth otic–occipitum complex, with no parietal crest and no parotic crest and process .... Speleomantes - Different from above ..........................................................................................................................................2 2. Middle depression with small foramina at the bottom and tuberculum at the posterior end of the prominentia semicircularis anterioris .................................................................................... Salamandrina - Different from above ..........................................................................................................................................3 3. Middle depression among prominentiae occupied by a fourth small prominentia ..................... Chioglossa - Different from above ..........................................................................................................................................4 4. In ventral view, fenestra basicranialis posterioris entirely covered by crista retrosellaris...........................5 - Fenestra basicranialis posterioris visible in ventral view...............................................................................6 5. Ventral spine present anterior to basicapsular commissure....................................................... Pleurodeles - Ventral spine absent .................................................................................................................... Salamandra 6. Crista retrosellaris covering the anterior half of the fenestra basicranialis ............................ Mertensiella - Crista retrosellaris absent.................................................................................................................................7 7. In lateral view, parotic process ventrally concave and small fenestra ovalis ............................... Calotriton - In lateral view, parotic process not ventrally concave and wide fenestra ovalis ............................................8 8. Middle depression with small foramina at the bottom................................................................... Euproctus - Smooth middle depression ................................................................................................................................9 9. In ventral view, low or absent medial crest ............................................................................... Ichthyosaura - In ventral view, medial crest high...................................................................................................................10 10. Parotic process rectangular in anterior and posterior views, minimally laterally extended...... Lissotriton - Parotic process laterally extended and sub-triangular in anterior and posterior views .............................11 11. Low parotic crest, equally high throughout its length............................................................ Ommatotriton - High parotic crest, generally higher close to the parietal crest ........................................................ Triturus Atlas+ 1. Strongly dorsoventrally compressed confluent occipital joints, with reduced horizontal odontoid process dorsal to them ....................................................................................................................................... Proteus - Different from above ..........................................................................................................................................2 2. Neural bulge or two articular surfaces instead of neural crest.......................................................................3 - No neural bulge or articular surfaces (walls of neural arch fused).................................................................4 3. Articular surface of the odontoid process unseparated ........................................................ Salamandrella - Articular surface of the odontoid process clearly separated.................................................... Speleomantes 4. High neural crest, posteriorly forked with lateral eversion .................................................. Salamandrina - Different from above ..........................................................................................................................................5 5. Horizontal dorsal edge of the neural arch in lateral view and neural crest low or absent...... Mertensiella - Different from above ..........................................................................................................................................6 6. Dorsal portion of the neural arch with several small foramina in posterior view ..................... Pleurodeles - Different from above ..........................................................................................................................................7 7. Triangular neural canal .............................................................................................................. Salamandra - Circular neural canal.........................................................................................................................................8 8. Low neural crest, neither posteriorly enlarged nor forked (or absent)...........................................................9 - Low neural crest, posteriorly enlarged ...........................................................................................................10 9. Neural spine present**..................................................................................................................... Euproctus - Neural spine absent......................................................................................................................... Calotriton 10. Low or absent secondary crests ............................................................................................... Ommatotriton - Marked secondary crests.................................................................................................................................11 11. Articular facets of odontoid process not contacting each other (large groove between them) Ichthyosaura - Articular facets of odontoid process contacting each other or slightly separated (narrow groove between them)..................................................................................................................................................12 12. Blade-like neural and secondary crests marked in anterior view .................................................... Triturus - Neural and secondary crests not marked in anterior view .......................................................... Lissotriton * Chioglossa is not included in the key because the only available atlas is too incomplete. **In one specimen ( MDHC 507) the neural spine is not present; the diagnosis is identical to the one of Calotriton . Precaudal vertebrae 1. Amphicoelous vertebrae ....................................................................................................................................2 - Opisthocoelous vertebrae ..................................................................................................................................4 2. No ventral crests and keels ...............................................................................................................................3 - Wide ventral crests and ventral keel................................................................................................... Proteus 3. Foramen on the lateral wall of the neural arch present.......................................................... Speleomantes - Foramen on the lateral wall of the neural arch absent ........................................................ Salamandrella 4. High, forked neural crest (with lateral lips)........................................................................... Salamandrina - Different from above ..........................................................................................................................................5 5. Dorsoventrally compressed vertebra (only one-fifth of the vertebra height formed by the neural arch dorsal to postzygapophyses), with low anterior zygapophyseal crests poorly visible in lateral view ......................6 - Different from above ..........................................................................................................................................8 6. Length approximately equal to width of the vertebra ............................................................... Salamandra - Elongate vertebrae.............................................................................................................................................7 7. Prezygapophyses not markedly laterally extended from the neural arch................................... Chioglossa - Prezygapophyses laterally projecting from the neural arch (vertebra with an overall hourglass-shape) ...................................................................................................................................................... Mertensiella 8. Anterior zygapophyseal crests contacting parapophyses or lamina of transverse processes or ventral half of diapophysis................................................................................................................................. Pleurodeles - Anterior zygapophyseal crests contacting dorsal half of diapophyses............................................................9 9. In anterior view, foramen at the base of parapophyses wide ................................................. Ommatotriton - In anterior view, foramen at the base of parapophyses small .......................................................................10 10. Dorsoventrally compressed vertebra (only one-fifth of the vertebra height formed by the neural arch dorsal to postzygapophyses) ........................................................................................................................... Triturus - One-third of the vertebra formed by neural crest/arch dorsal to postzygapophyses ...................................11 11. Wide, equidimensional prezygapophyses (circular or quadrangular)........................................... Calotriton - Elliptical prezygapophyses..............................................................................................................................12 12. High, posteriorly forked neural crest and condyle visible for most of its length in dorsal view .. Euproctus - Different from above ........................................................................................................................................13 13. In dorsal view, medial edges of the prezygapophyseal facets generally anteriorly diverging........ Ichthyosaura - In dorsal view, medial edges of the prezygapophyseal facets generally parallel......................... Lissotriton Caudal vertebrae 1. Amphicoelous vertebrae ....................................................................................................................................2 - Opisthocoelous vertebrae ..................................................................................................................................4 2. Posterior, dorsal bulge present ..........................................................................................................................3 - Dorsal bulge absent, and forked posterior edge of the neural arch ................................................... Proteus 3. Transverse processes expanded in dorsal view and slightly dorsally concave in anterior view .................................................................................................................................................... Speleomantes - Transverse processes sub-rectangular in dorsal view and ventrally pointing in anterior view ................................................................................................................................................. Salamandrella 4. Low and wide neural arch dorsal to postzygapophyses (neural arch dorsal to postzygapophyses flattened) ............................................................................................................................................................................5 - High and narrow neural arch dorsal to postzygapophyses (neural arch dorsal to postzygapophyses not flattened) ............................................................................................................................................................6 5. High neural and haemal crest .................................................................................................... Mertensiella - Low haemal crest, and neural crest high only in its mid-length............................................... Salamandra 6. M-shaped transverse processes and anterior and posterior ventral crests forming an angle <130° in lateral view........................................................................................................................................... Salamandrina - Different from above ..........................................................................................................................................7 7. Posterior area of the dorsal surface of the neural arch and of the ventral surface of the haemal arch perforated ....................................................................................................................................... Pleurodeles - Different from above ..........................................................................................................................................8 8. Wide foramen on the lateral surface of the haemal arch ................................................................................9 - Small foramen or no foramen on the lateral surface of the haemal arch .....................................................10 9. Height/length ratio ~1.3–1.4, and transverse processes in lateral view, laminar and anteroventrally inclined ...................................................................................................................................... Ommatotriton - Height/length ratio <1.3, and transverse processes different from above ....................................... Triturus 10. Transverse processes triangular in anterior view .......................................................................... Euproctus - Transverse processes different from above ....................................................................................................11 11. Transverse processes posteriorly concave in lateral view ............................................................. Calotriton - Transverse processes different from above ....................................................................................................12 12. Height/length ratio> 1.4 ................................................................................................ Lissotriton Uulgaris - Height/length ratio ~1.3–1.4 ............................................................. Ichthyosaura /other Lissotriton spp.