DOI: 10.5061/dryad.bvq83bkfx
title: Data from: Extreme neck elongation evolved despite strong developmental constraints in bizarre Triassic reptiles – implication for neck modularity in archosaurs

description: The Triassic radiation of vertebrates saw the emergence of the modern
 vertebrate groups, as well as numerous extinct animals exhibiting
 conspicuous, unique anatomical characteristics. Among these, members of
 Tanystropheidae (Reptilia: Archosauromorpha) displayed cervical vertebral
 elongation to an extent unparalleled in any other vertebrate.
 Tanystropheids were exceptionally ecologically diverse and had a wide
 spatial and temporal distribution. This may have been related to their
 neck anatomy, yet its evolution and functional properties remain poorly
 understood. We used geometric morphometrics to capture the intraspecific
 variation between the vertebrae comprising the cervical column among early
 archosauromorphs, to trace the evolutionary history of neck elongation in
 these animals. Our results show that the cervical series of these reptiles
 can be divided into modules corresponding to those of extant animals.
 Tanystropheids achieved neck elongation through somite elongation and a
 shift between cervical and thoracic regions, without presacral vertebrae
 count increase - contrary to crown archosaurs. This suggests a peculiar
 developmental constraint that strongly affected the evolution of
 tanystropheids. The data obtained just at the base of the archosauromorph
 phylogenetic tree is crucial for further studies on the modularity of
 vertebral columns of not only Triassic reptile groups but extant and other
 extinct animals as well.
description: This dataset contains all of the untransformed morphometric data
 used in the study Rytel et al. 2024. Landmarks (LMs)
 used in the main (two-dimensional) analysis were digitised onto specimen
 photographs in the tpsDig v2.31 software in accordance with a landmark set
 encompassing the outline of the vertebrae in lateral view. The landmarks
 cover the maximal extent of characteristic osteological features –
 vertebral centrum, neural spine, pre- and postzygapophysis. These points
 are considered to be homologous for all of the studied taxa. The chosen
 landmarks (together with semilandmarks) cover most of the shape of the
 vertebrae. Moreover, they are (aside from LM5 in some cases) extremely
 easy to locate, providing high repeatability potential.
 Exact definitions of the true landmarks contained within the
 landmark set are listed below: 1.         
 Ventral-posterior edge of the centrum 2.         
 Ventral-anterior edge of the centrum 3.          Point
 of maximum curvature between prezygapophysis and the anterior edge of the
 centrum 4.          Dorsal-anterior edge of the
 prezygapophysis 5.          Point of maximum curvature
 between prezygapophysis and neural spine 6.         
 Dorsal-anterior edge of the neural spine 7.         
 Dorsal-posterior edge of the neural spine 8.         
 Dorsal-posterior edge of the postzygapophysis
 Semilandmark lines encompassed the following number of
 semilandmarks: 16 ( between LM1 and LM2), 7 (LM2-LM3), 8 (LM3-LM4), 9
 (LM4-L5), 6 (LM5-LM6), 14 (LM6-LM7), 13 (LM7-LM8). Most
 of the other data are contained within the associated manuscript and the
 supplementary material.
description: The .dat files can be opened with the free PAST software for
 Windows only (https://past.en.lo4d.com/windows). It can also be opened with a simple text editor.
description: # Data from: Extreme neck elongation evolved despite strong developmental
 constraints in bizarre Triassic reptiles – implication for neck modularity
 in archosaurs --- This dataset contains the raw (untransformed) x/y data
 for the landmarks digitised onto the archosauromorph vertebrae photographs
 in the tpsDig v2.31 software. ## Description of the Data and file
 structure The dataset contains seven .dat files that correspond to data
 gathered for four genera of Triassic archosauromorphs:
 **Macrocnemus_bassanii_raw** - *Macrocnemus bassanii*. Contains xy data
 for 83 landmark points gathered from 2D images.
 **Macrocnemus_fuyuanensis_raw** - *Macrocnemus fuyuanensis*. Contains xy
 data for 83 landmark points gathered from 2D images.
 **Prolacerta_broomi_raw** - *Prolacerta broomi*. Contains xy data for 83
 landmark points gathered from 2D images.
 **Prolacerta_broomi_supplement_raw** - *Prolacerta broomi*. Contains xy
 data for 64 landmark points gathered from 2D images. The landmark set was
 reduced from 83 to 64 points to allow for a broader sampling of damaged
 specimens. **Protorosaurus_speneri_raw** - *Protorosaurus speneri*.
 Contains xy data for 83 landmark points gathered from 2D images.
 **Tanystropheus_spp._raw** - *Tanystropheus* spp. (*T*. ‘*conspicuus*’,
 *hydroides*, *longobardicus*, sp.). Contains xy data for 83 landmark
 points gathered from 2D images.
 **Tanystropheus_conspicuus_2Dvs3D_combined_transformed** - *Tanystropheus*
 spp. (*T*. ‘*conspicuus*’, *hydroides*, *longobardicus*, sp.). Contains
 xyz data for 83 landmark points gathered from 2D images and 3D models. A
 cell with the third dimension (z) value of 0 was added to each of the 2D
 landmarks. This allowed both datasets to be superimposed together. They
 were then mean cantered by removing means from the respective shape data
 (2D or 3D) in each column. The rows marked with red are two-dimensional
 data, while the rows marked with blue are three-dimensional data. Both of
 these have been transformed by Procrustes superimposition. Within the data
 set, each row represents a singular vertebra, with a name coded as X(first
 letter of the genus name)xyz(first three letter of the species
 name)_specimen_number_xy(position in the neck - if possible to determine).
 ## Sharing/access Information NA