Trachelosaurus fischeri Broili, 1918

Spiekman, Stephan N. F., Ezcurra, Martín D., Rytel, Adam, Wang, Wei, Mujal, Eudald, Buchwitz, Michael & Schoch, Rainer R., 2024, A redescription of TraCheloSaUrUS fiSCheri from the Buntsandstein (Middle Triassic) of Bernburg, Germany: the first European DinoCephaloSaUrUS-like marine reptile and its systematic implications for long-necked early, Swiss Journal of Palaeontology (10) 143 (1), pp. 1-33 : 8-10

Trachelosaurus fischeri Broili, 1918 3

1902 “ Protorosaurus -ähnli- v. Huene, p 8–10; Fig. 4 ches Reptil "

1917 Trachelosaurus Berliner & PÜtter, Fischeri * p. 767 *authorship

given to Broili & Fischer

2 While the original description was predominantly cited as if published in 1917, it was contained within a journal issue printed in 1918.

3 While the genus name could have been erected by either of the authors, the species name was given by F. Broili to commemorate E. Fischer, who died in 1914.

1918 Trachelosaurus Fischeri Broili & Fischer ,throughout text; Figs. 1–7 , 15; plates 31–32

1919 Trachelosaurus Fischeri Abel , p. 482–483

1920 Trachelosaurus Fischeri Abel , p. 375

1921 Trachelosaurus Edinger , p. 204

1922 Trachelosaurus Fischeri Cossmann , p. 91

1923 Trachelosaurus Nopcsa , p. 68

1924 Trachelosaurus von Arthaber , p. 442

1927 Trachelosaurus Fischeri Weigelt ,p. 54,118 (in the 1989 edition)

1928 Trachelosaurus Nopcsa , p. 172

1928 Trachelosaurus Fischeri Schmidt , p. 393;

Fig. 1104

1932 Trachelosaurus v. Zittel, p. 285

1933 Trachelosaurus Gadow ,p. 329

1935 Trachelosaurus fischeri Kuhn ,p. 28

1944 Trachelosaurus fischeri v. Huene, through-

out text

1948 Trachelosaurus v. Huene, p. 102

1951 Trachelosaurus Watson , p. 169

1952 Trachelosaurus Fischeri Lang & v. Huene, p. 15

1954 Trachelosaurus v. Huene, p. 229; Fig. 2d

1955 Trachelosaurus Vaughn ,p. 435–436, 448

1955 Trachelosaurus Peyer & Kuhn-Schnyder , p. 598

1956 Trachelosaurus v. Huene, p. 648, 683

1956 Trachelosaurus Romer , p. 432,657; Figs. 122L, 131D, 139O, 140X

1957 Trachelosaurus Watson , Fig. 23

1961b Trachelosaurus Kuhn ,p. 5

1963 Trachelosaurus fischeri Kuhn ,p. 3, 5–7

1967 Trachelosaurus fischeri Appleby et al. , p. 704

1969 Trachelosaurus Carroll , p. 166

1971 Trachelosaurus fischeri Kuhn ,p. 12; Figs. 20a/1, 41b/8

1973 Trachelosaurus Wild , p. 28

1975 Trachelosaurus fischeri Kuhn ,p. 8; Fig. 3

1982 Trachelosaurus fischeri Mader , Table 2

1988 Trachelosaurus Carroll , p. 619

1988 Trachelosaurus Evans , p. 227–228

1994 Trachelosaurus Renesto , p. 286

1997 Trachelosaurus fischeri Benton & Allen , Table 1; text-Fig. 16

1997 Trachelosaurus Jalil , throughout text

1999 Trachelosaurus Borsuk-Białynicka et al. , p. 182; Table 1

2000 Trachelosaurus fischeri Rieppel , p. 110

2003 Trachelosaurus Rieppel et al. , throughout text

2008 Trachelosaurus Hone & Benton , throughout text

2009 Trachelosaurus Gottmann-Quesada & Sander , throughout text

2015 Trachelosaurus fischeri Hauschke & Mertmann ,

p. 344

2016 Trachelosaurus Ezcurra , p. 311

2018 Trachelosaurus Hauschke , p. 286

2018 Trachelosaurus fischeri Schoch ,p. 108, 111

2019 Trachelosaurus fischeri Schoch ,p. 58

2021 Trachelosaurus fischeri Hauschke et al. , p. 333,

388

2021 Trachelosaurus fischeri Spiekman et al. ,

throughout text

2022 Trachelosaurus fischeri Ezcurra et al. , p. 5

Holotype. MLU.GeoS.1612, a partially disarticulated skeleton comprising a few isolated skull remains, including a right premaxilla, much of the presacral vertebral column, two sacral vertebrae, several caudal vertebrae, an extensive gastral basket, a right ilium, right? pubis, left? femur, and at least one probable metatarsal.

Diagnosis. A tanysaurian archosauromorph that is defined by the following combination of features (autapomorphies among Triassic archosauromorphs indicated by an asterisk): elongate vertebral column that consists of at least 21 cervical and 27 dorsal vertebrae; neural spines on both the cervical and dorsal vertebrae that are transversely expanded at their distal ends with strongly developed rugosities*; cervical ribs with bifurcating shafts that are short, not or barely extending beyond the length of its corresponding vertebra*; anterior to mid-dorsal vertebrae with very wide, ‘wing-like’ transverse processes; a barrel-shaped torso formed by widely rounded, almost uniformly holocephalous dorsal ribs; an ilium without a preacetabular process; and a stocky femur without a curved shaft.

Horizon. Te type and only specimen of Trachelosaurus fischeri was found in a platy sandstone unit within the Chirotheriensandstein, upper part of the Solling Formation (topmost Middle Buntsandstein, probably of earliest Anisian age, see Schoch, 2019; Bachmann et al., 2021).

Locality. Merkel’s quarry, Bernburg an der Saale, Saxony-Anhalt, central Germany.

Ontogenetic assessment. Trachelosaurus fischeri is currently known from a single specimen, MLU. GeoS.1612, comprising one individual (see below). In both the anteriormost cervical vertebra and mid-dorsal vertebrae, the neural arches and centra are unfused or disarticulated. Furthermore, the proximal and distal ends of the femur are poorly ossified. Tese features are often indicative of skeletal immaturity in diapsids ( Griffin et al., 2021). However, they can also represent typical paedomorphic traits related to aquatic adaptations seen in skeletally mature marine reptiles, including Dinocephalosaurus orientalis ( Griffin et al., 2021; Rieppel, 1989; Spiekman et al., 2024). Considering the presence of several features indicative of an aquatic lifestyle in Trachelosaurus fischeri (high presacral vertebral count, straight femur, and absence of preacetabular process of the ilium), and its close affinities to the marine Dinocephalosaurus orientalis (see below), the latter interpretation is very likely. Terefore, these features are not reliable indicators of relative ontogenetic age for this individual. Te presence of strongly rugose neural spines on the presacral vertebrae could represent some indication of maturity, but this cannot be stated confidently.

Remarks. Te most recent definition of Tanystropheidae Camp, 1945 was formulated by Dilkes (1998, page 529): “the most recent common ancestor of Macrocnemus , Tanystropheus , and Langobardisaurus and all of its descendants”. Considering the discovery of many new tanystropheid taxa in recent years, as well as the results of our phylogenetic analyses and the novel definitions of Tanysauria clade nov. and Trachelosauridae Abel, 1919 , we propose a revised definition for Tanystropheidae that is stem-based: the most inclusive clade containing Tanystropheus longobardicus ( Bassani, 1886) but not Trachelosaurus fischeri Broili, 1918 , Dinocephalosaurus orientalis Li, 2003 , Protorosaurus speneri von Meyer, 1832 , or Prolacerta broomi Parrington, 1935 . Tis is a maximum clade definition.

Phylocode registration number. Tanystropheidae is identified in the international clade names repository as registration number 1040.

Description

MLU.GeoS.1612 consists of seven slabs that can be fitted together to form a single block ( Fig. 2B ). Te majority of the remains of Trachelosaurus fischeri , including virtually all pre-caudal axial elements, are closely associated in MLU.GeoS.1612.A-B ( Fig. 3 ). Additional remains, including cranial elements and a partial gastral basket, are scattered across MLU.GeoS.1612.C-G ( Fig. 4 ). Te slabs additionally preserve indeterminate remains of actinopterygian fishes, as well as several footprints resembling Capitosauroides bernburgensis and a tetrapod ichnotaxon possibly produced by therapsid trackmakers that was described from an unknown locality in the same area ( Buchwitz et al., 2020; Haubold, 1971). Te discovery of several tetrapod footprints while examining the slabs (in addition to those previously reported by Broili & Fischer, 1918) requires a more detailed description and analysis that are outside the scope of the present work ( Fig. 2B ).

Figures

Fig. 4 Overview of MLU.GeoS.1612.C-G,preserving the cranial and proximal caudal remains, as well as a tentatively identified pubis and partial gastral basket.The rib marked with †‡ corresponds to the rib that is indicated the same in Table 4. Abbreviations: car, caudal rib; cav, caudal vertebra; dr, dorsal rib; fisc, fish scales; fr v, fragmentary vertebra; gas,gastralia; na, nasal;pmx, premaxilla; po, postorbital; pof, postfrontal; pub, pubis

Fig. 1 Geographic and geological setting. Locality and stratigraphic context of Merkel’s Quarry, where Trachelosaurus fischeri was found. Modified from Schoch (2019)

Fig. 2 Overview of MLU.GeoS.1612 and its sedimentary features.A, Historical label on the slab.B, Overview of MLU.GeoS.1612, the holotype of Trachelosaurus fischeri; the bracketed lower case letters correspond to the different slabs of which the specimen is composed.The asterisks (*) indicate tetrapod footprints preserved on the slabs.C–D Slab in cross-section, with trough cross-lamination (C) and the two intervals with an arrow pointing at their boundary (D). E Sinuous and ramified structures on the top surface (opposite to the surface preserving bones and footprints), including a close-up on the right. F Round structures.G Squared structure.H Tetrapod footprint (left manus) previously mentioned in Broili and Fischer (1918). Structures in F–H are in convex hyporelief,and their location is marked with matching upper case letters on the overview of the specimen in B

Fig. 3 Overview of MLU.GeoS.1612.A–B preserving the majority of the presacral vertebrae and appendicular elements. Cervical vertebrae are indicated with capitalised letters, dorsal and sacral vertebrae are indicated with lower case letters, blue dots indicate bifurcated cervical ribs.The element indicated with an asterisk represents a badly broken cervical vertebra, which could be identified based on plate 31 of Broili and Fischer (1918). The two ribs indicated with † and ‡, respectively, correspond to those listed in Table 4. Abbreviations: aue,autopodial element; cav, caudal vertebra; fe, femur; fr v, fragmentary vertebra; il, ilium; mt, metatarsal; sv, sacral vertebra

Fig. 5 Close-ups of the cranial elements of Trachelosaurus fischeri. A Right premaxilla in lateral view. B The posterior of the two preserved premaxillary teeth. C Possible nasal. D Possible postorbital. E Possible postfrontal. Abbreviations: anp, anterior process; conc, concavity; latp, lateral process; ponp, postnarial process; pop, posterior process; prnp, prenarial process

Fig. 6 Close-ups of selected cervical vertebrae and ribs of Trachelosaurus fischeri. A Anteriormost preserved cervical vertebrae (elements A–C), including the tentatively identified axis and possible atlantal elements. B Cervical ribs with bifurcating distal ends. C Mid-cervical vertebrae (elements L–N). Abbreviations: at, atlantal element; atna, atlantal neural arch; atr, atlantal rib, axc, axis centrum; axna, axis neural arch; cap, capitulum; cv,cervical vertebra; cvr, cervical rib; diap,diapophysis;epp, epipophysis; feap,free-ending anterior process; fs,fish scale; lam, lamina; ns, neural spine; pap, parapophysis;pdp, posterodorsal process; poz, postzygapophysis; prz, prezygapophysis; pvp, posteroventral process; rug, rugosity; tub, tuberculum

Fig. 7 Close-ups of selected dorsal and sacral vertebrae and ribs of Trachelosaurus fischeri. A Anterior and mid-dorsal vertebrae (elements a-o). B Posterior dorsal vertebrae (elements s-u). C Anteriormost dorsal rib. D Posteriormost dorsal vertebrae and sacral vertebrae.Abbreviations: cap, capitulum; ce, centrum; diap, diapophysis; lam, lamina; na, neural arch; nc, neural canal; ns, neural spine; pap, parapophysis;pcdl, posterior centrodiapophyseal lamina; podl, postzygodiapophyseal lamina; poz, postzygapophysis; prdl, prezygodiapophyseal lamina; prz, prezygapophysis;rf, rib facet; rug, rugosity; sv, sacral vertebra; tub, tuberculum; tvp, transverse process