DOI: 10.5061/dryad.sqv9s4ndn
title: Data for: A diminutive Tyrannosaur lived alongside <em>Tyrannosaurus rex</em>

description: Whether Nanotyrannus lancensis, a putative species of small tyrannosaurid,
 represents a distinct taxon or an immature Tyrannosaurus rex is a
 decades-long controversy. The N. lancesis holotype is an isolated skull
 and ceratobranchials, but limb osteohistology of Nanotyrannus-like
 individuals implies that these individuals were immature Tyrannosaurus,
 suggesting that the Nanotyrannus holotype is also immature. We demonstrate
 for the first time that ceratobranchial (‘hyoid’) histology is useful for
 ontogenetic assessment in extant and extinct archosaurs. The
 ceratobranchial histology of the N. lancensis holotype indicates that it
 was nearing or had reached skeletal maturity, suggesting that it is
 taxonomically distinct from the coeval Tyrannosaurus rex and that Hell
 Creek (and equivalent) ecosystems supported a diverse assemblage of
 predatory dinosaurs approaching the K-Pg extinction event.
description: # Data for: A diminutive Tyrannosaur lived alongside *Tyrannosaurus rex*
 [https://doi.org/10.5061/dryad.sqv9s4ndn](https://doi.org/10.5061/dryad.sqv9s4ndn) ## Description of the data and file structure The filenames of the associated whole-slide histological images reflect the taxon, specimen number, element, sampling location (if applicable), light regime, and magnification; "Genus_species_Museum####_Element_SamplingLocation_LightAbbreviation_Magnification.tif" 'Hyoid' as an element refers to ceratobranchial I. Light regime abbreviations: PP - Plane-polarized light XP - Cross-polarized light XPR - Cross-polarized light with a lambda retarder R - Reflected light OSEM - Optical shadow effect mode (a feature in the Keyence VHX-7100 digital microscope) Light - in addition to one of the above light regimes, this scan included either increasing brightness either digitally or by wetting the slide Example: Struthio_camelus_YPM112434_rightHyoid_cranialsample_XPR_200x.tif Ostrich (*Struthio camelus*), specimen YPM 112434, right hyoid (ceratobranchial I), the cranial sampling location, cross-polarized light with a lambda retarder, 200x magnification All filenames that include "Wagner" are images of slides made via automated grinder by Wagner Petrographics, Inc. All other slides were made by hand. ### Files and variables #### File: Alligator_mississippiensis.zip **Description:** Whole-slide images of *Alligator mississippiensis* bone histology #### File: Struthio_camelus.zip **Description:** Whole-slide images of *Struthio camelus* bone histology #### File: Allosaurus_fragilis.zip **Description:** Whole-slide images of *Allosaurus fragilis* bone histology #### File: Allosaurus_jimmadseni.zip **Description:** Whole-slide images of *Allosaurus jimmadseni* bone histology #### File: Coelophysis_bauri.zip **Description:** Whole-slide images of *Coelophysis bauri* bone histology #### File: Edmontosaurus_sp.zip **Description:** Whole-slide images of *Edmontosaurus sp.* bone histology #### File: Paleosuchus_palpebrosus.zip **Description:** Whole-slide images of *Paleosuchus palpebrosus* bone histology #### File: Eutyrannosaurians.zip **Description:** Whole-slide images of *Tyrannosaurus rex* (LACM specimens) and an indeterminate eutyrannosaur (SWAU individual) #### File: Nanotyrannus_lancensis.zip **Description:** Whole-slide images of *Nanotyrannus lancensis* bone histology. One whole slide in the "Caudal" subfolder, with "CGMtraced" in the file name, contains a whole slide image with a cortical growth mark (CGM) traced around the cortex, as in Fig. S1. The whole-slide version of this figure permits others to trace this CGM on the large, high-resolution image.