DOI: 10.5061/dryad.cfxpnvxhh
title: Data for: A phylogeny for Heterostraci (stem-gnathostomes)

description: The armoured jawless fishes (“ostracoderms”) are major and widespread
 components of middle Palaeozoic ecosystems. As successive branches on the
 gnathostome stem lineage, they reveal the early sequences of vertebrate
 evolution, including the assembly of the vertebrate skeleton. This is
 predicated however, on understanding of their diversity and
 interrelationships. The largest ostracoderm clade, the Pteraspidomorphi,
 is often reconstructed as sister taxon to other boney vertebrates yet they
 lack a cladistic phylogenetic framework, in particular the heterostracans.
 Problematic heterostracans with a tessellate headshield
 (‘tessellate-basal’ model) are often regarded as the plesiomorphic
 condition for the clade but no phylogenetic analysis has included these
 taxa. Here we review the Heterostraci and present their first
 comprehensive phylogenetic analysis (131 heterostracan taxa and 55
 outgroup taxa). Heterostraci are recovered as monophyletic, and forming a
 clade together with the Ordovician Pteraspidomorphi near the root of the
 gnathostome crown group in parsimony analyses. The heavily armoured
 Amphiaspida are recovered as sister taxon to all other Heterostraci.
 Within the Heterostraci, the Psammosteida are nested within the
 Pteraspidiformes, which are sister group to the Traquairaspidida, whist
 Cyathaspidida form a monophyletic group. The results presented here are
 the first phylogenetic hypotheses of heterostracan relationships and it is
 hoped a first step into an accurate interpretation of character evolution
 in this crucial episode of vertebrate evolution.
description: # Data for: A phylogeny for Heterostraci (stem-gnathostomes)
 [https://doi.org/10.5061/dryad.cfxpnvxhh](https://doi.org/10.5061/dryad.cfxpnvxhh) ## Description of the data and file structure Morphological Matrices in 1. Nexus format with character names and character settings (new_het3.nex) 2. TNT format with discretised continuous characters and TNT search commands and settings (new_het3.tnt) 3. TNT format with raw continuous characters and TNT search commands and settings (new_het3cont) 4. Nexus format with Mr Bayes search commands (new_het3 MrBayes.nex) 5. Character list with supplementary figures (Supplementary_Information._Randle_et_al_2025_v2.pdf) 6. Stratigraphic age range data used for construction of figure 6 (Thesis_Heterostraci_Strat3.txt) Note: Taxon name *Helaspis* was used in early earlier versions of this manuscript but has been superceded by *Clavulaspis* (Elliott D. et al. 2020 The last pteraspids (Vertebrata, Heterostraci): new material from the Middle Devonian of Alberta and Idaho. Journal of Paleontology. 94 [https://doi.org/10.1017/jpa.2020.9](https://doi.org/10.1017/jpa.2020.9) ### Files and variables #### File: new_het3.nex **Description:** Morphological matrix in nexus format with character names and settings #### File: new_het3.tnt **Description:** Morphological matrix in TNT format with discretised continuous characters with search commands and settings #### File: new_het3cont.txt **Description:** Morphological matrix in TNT format with raw continuous characters with search commands and settings #### File: new_het3_MrBayes.nex **Description:** Morphological matrix in nexus format with Mr Bayes search commands and settings #### File: Supplementary_Information._Randle_et_al_2025_v2.pdf **Description:** Character List and Supplementary figures 1 and 2 ### Usage Notes .nex, .tnt, and .txt files can all be viewed in a standard text editor .pdf can be opened in any standard .pdf viewer