DOI: 10.6086/d1hx1d
title: Data from: Absolute axial growth and trunk segmentation in the early Cambrian trilobite Oryctocarella duyunensis

description: A short stratigraphic interval near Bulin in western Hunan (China) yields
 multiple specimens of the ~514 Ma old oryctocarine trilobite Oryctocarella
 duyunensis. Size data obtained from these specimens indicates that, from
 meraspid degree 1 onwards, degrees represent successive instars. Meraspid
 growth persisted until a terminal stage was reached, providing the first
 example of determinate growth in trilobites and, notably, in an early
 Cambrian species. The sample contains three varieties of such terminal
 stages, recognized as holaspids, with 9, 10, or 11 thoracic segments
 respectively. During the meraspid phase growth rates were not constant in
 this species. The pattern of growth seen in the Bulin assemblage differs
 modestly from that reported in the same species from two other localities,
 attesting to microevolutionary variation in developmental patterns among
 these collections.
description: Data from:<br> Dai T., Hughes N.C., Zhang X.-L, Fusco G.
 (2021). Absolute axial growth and trunk segmentation in the early Cambrian
 trilobite Oryctocarella duyunensis. Paleobiology.<br> [Dataset 1 and
 2 have also been used in Dai et al.(2021). Development of the early
 Cambrian oryctocephalid trilobite Oryctocarella duyunensis from western
 Hunan, China. Journal of Paleontology.] DATASET
 1<br> Dataset 1 comprises 968 specimens that permitted measurement
 of their sagittal dorsal length and the number of thoracic
 segments Legend of dataset 1<br> NTH    Number of
 THoracic segments<br> BL    Body Length (in millimeters)<br>
 lnBL    Natural logarithm of Body Length DATASET
 2<br> Dataset 2 is a subset of dataset 1 which comprises 643
 specimens where, in addition, segment number in the pygidia could also be
 counted with confidence Legend of dataset 2<br>
 NTH    Number of THoracic segments<br> NPY    Number of PYgidial
 segments<br> BL    Body Length (in millimeters)<br> lnBL  
  Natural logarithm of Body Length DATASET 3<br>
 Dataset 3 is a subset of dataset 2 which comprises 337 specimens in which
 landmark-based measurements could be taken for an array of
 characters Legend of dataset 3<br> Stage  
  Developmental stage (instar) assignment based on the number of thoracic
 segments (see text)<br> morph    Morph description based on the
 number of thoracic segments (first figure) and the number of pygidial
 segments (second figure)<br> NTH    Number of THoracic
 segments<br> NPY    Number of PYgidial segments<br> CCS  
  Cephalic Centroid Size<br> CEL    CEphalic Length    <br>
 TRL    TRunk Length     <br> PYL    PYgidial Length     <br>
 PCj    Distance of the Posterior boundary of Cephalic segment j from
 cephalon anterior boundary (PC0= frontal piece; PC6=CEL)   [corresponds to
 the cumulative segment length of the cephalon until cephalic segment j
 included]<br> PTi    Distance of the Posterior boundary of Trunk
 Segment i from cephalon/trunk boundary  [corresponds to the cumulative
 segment length of the trunk until trunk segment i included]
 All measures are in millimeters Colors refer
 to segmental units of different body parts:<br> Olive green  
  Frontal piece<br> Green             Cephalon to the exclusion of
 the frontal piece<br> Dark blue       Thorax<br> Blue         
      Pygidium to the exclusion of the terminal piece<br> Purple     
       Terminal piece Note that in Fig. 1 junctions
 within the thorax are shown by pink diamonds, and those within the
 pygidium, and its posterior, in orange.