[dinosaur] Limb identity networks + feather color and flight + Mourasuchus + coloration + tetrapod evolution.

Ben Creisler
[email protected]

Some recent non-dino papers that may be of interest:


Free pdf:

Elena F. Boer, Hannah F. Van Hollebeke, Sungdae Park, Carlos R. Infante,
Douglas B. Menke & Michael D. Shapiro (2019)
Pigeon foot feathering reveals conserved limb identity networks.
Developmental Biology (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.ydbio.2019.06.015&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=2DcxLW_MqpMZ0R4CylqXjU-bdT0CyqCUKMtXe4jlKbU&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_pii_S001216061930274X&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=4eg21SHNFCW_b6JenjoUVCHBVdv4pWGrChEneLO1Ymg&e= 


Highlights

Feathered feet of pigeons result from a partial change in hindlimb identity.
PITX1-and TBX5-responsive genes are misexpressed in feathered feet of
pigeons.
Some misexpressed "feathered feet" genes also distinguish forelimbs and
hindlimbs.
Differentially expressed genes include TFs and other gene classes.
Comparisons among amniotes reveals conserved PITX1 and TBX5-responsive
genes.

Abstract

The tetrapod limb is a stunning example of evolutionary diversity, with
dramatic variation not only among distantly related species, but also
between the serially homologous forelimbs (FLs) and hindlimbs (HLs) within
species. Despite this variation, highly conserved genetic and developmental
programs underlie limb development and identity in all tetrapods, raising
the question of how limb diversification is generated from a conserved
toolkit. In some breeds of domestic pigeon, shifts in the expression of two
conserved limb identity transcription factors, PITX1 and TBX5, are
associated with the formation of feathered HLs with partial FL identity. To
determine how modulation of PITX1 and TBX5 expression affects downstream
gene expression, we compared the transcriptomes of embryonic limb buds from
pigeons with scaled and feathered HLs. We identified a set of
differentially expressed genes enriched for genes encoding transcription
factors, extracellular matrix proteins, and components of developmental
signaling pathways with important roles in limb development. A subset of
the genes that distinguish scaled and feathered HLs are also differentially
expressed between FL and scaled HL buds in pigeons, pinpointing a set of
gene expression changes downstream of PITX1 and TBX5 in the partial
transformation from HL to FL identity. We extended our analyses by
comparing pigeon limb bud transcriptomes to chicken, anole lizard, and
mammalian datasets to identify deeply conserved PITX1- and TBX5-responsive
components of the limb identity program. Our analyses reveal a suite of
predominantly low-level gene expression changes that are conserved across
amniotes to regulate the identity of morphologically distinct limbs.

===

Svana Rogalla , Liliana D'Alba , Ann Verdoodt  and Matthew D. Shawkey (2019)
Hot wings: thermal impacts of wing coloration on surface temperature during
bird flight
Journal of the Royal Society Interface 16(156): 20190032
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1098_rsif.2019.0032&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=fc5BghYpMrd8V3cB9DmKcRjXst64CsjEt5-Q2EO46AM&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_10.1098_rsif.2019.0032&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=TaGHbHLsh7307tXLkpX9Bt3jQFB9QysRxc-GHC-ZYgo&e= 

Recent studies on bird flight propose that hotter wing surfaces reduce skin
friction drag, thereby improving flight efficiency (lift-to-drag ratio).
Darker wings may in turn heat up faster under solar radiation than lighter
wings. We used three methods to test the impact of colour on wing surface
temperature. First, we modelled surface temperature based on reflectance
measurements. Second, we used thermal imaging on live ospreys (Pandion
haliaetus) to examine surface temperature changes with increasing solar
irradiance. Third, we experimentally heated differently coloured wings in a
wind tunnel and measured wing surface temperature at realistic flight
speeds. Even under simulated flight conditions, darker wings consistently
became hotter than pale wings. In white wings with black tips, the
temperature differential produced convective currents towards the darker
wing tips that could lead to an increase in lift. Additionally, a
temperature differential between wing-spanning warm muscles and colder
flight feathers could delay the flow separation above the wing, increasing
flight efficiency. Together, these results suggest that wing coloration and
muscle temperature both play important roles in modulating wing surface
temperature and therefore potentially flight efficiency.
Study suggests dark-colored wing feathers may help birds fly more
efficiently
https://urldefense.proofpoint.com/v2/url?u=https-3A__phys.org_news_2019-2D07-2Ddark-2Dcolored-2Dwing-2Dfeathers-2Dbirds-2Defficiently.html&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=GVb-oMW5TC8auuaTeJos-TyyU0AULVCPU51MBNgLMxY&e= 

===

Free pdf:

Giovanne M. Cidade, Douglas Riff, Jonas P. de Souza-Filho, and Annie
Schmaltz Hsiou (2019)
A reassessment of the osteology of Mourasuchus amazonensis Price, 1964 with
comments on the taxonomy of the species.
Palaeontologia Electronica 22.2.44A: 1-23.
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.26879_893&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=bVPAbL_sAzfUoVao4p1k-bBF-5x99vdAox0W2XxfZh8&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__palaeo-2Delectronica.org_content_2019_2602-2Dmourasuchus-2Damazonensis&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=wTw7bgKXUyw-XTtSY5TWOs_VPmScQhcttUeqF747D0Q&e= 


This study is a thorough assessment on the morphology and taxonomy of
Mourasuchus amazonensis, a fossil crocodylian of the Caimaninae clade from
the late Miocene Solimões Formation of Brazil. A thorough redescription of
the holotype of the species (DGM 562-R, a nearly complete skull with an
associated incomplete left mandible) is performed together with the
redescription of the specimen UFAC-1424, a posterior portion of the skull
with associated mandibular remains, and the description of the specimen
LACM-160157, also a posterior portion of the cranium. As such, this paper
brings the most comprehensive osteological study of M. amazonensis to be
performed to date, enabling a thorough taxonomic reassessment of the
species in question. This reassessment confirmed M. amazonensis as a valid
species, with two autapomorphies and two other distinctive characters.
UFAC-1424 and LACM-160157 are assigned as Mourasuchus cf. M. amazonensis,
pending further studies on the taxonomy of the species in order to clarify
whether these specimens belong to the same species as DGM 526-R.
Additionally, implications of the morphology observed in M. amazonensis for
the taxonomic status of other Mourasuchus species are also discussed,
especially with respect to M. nativus, which is currently a junior synonym
of M. arendsi.

===


Free pdf:

Jindřich Brejcha, José Vicente Bataller, Zuzana Bosáková, Jan Geryk,
Martina Havlíková, Karel Kleisner, Petr Maršík  and Enrique Font (2019)
Body coloration and mechanisms of colour production in Archelosauria: the
case of deirocheline turtles.
Royal Society Open Science 6(7):  190319
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1098_rsos.190319&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=l0WtNyg19SDvKndN_XsqRNDRbDos3Uk5asqwB2gVtpw&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_10.1098_rsos.190319&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=37Jx654yeNUPnQBtJGqCsbBeAEs9ibplWGhknHOj7IU&e= 
Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_pdf_10.1098_rsos.190319&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=w2faz84scP57H7_MjjzbRnS0-9XSVVqsuuGl5TWaoXY&e= 


Animal body coloration is a complex trait resulting from the interplay of
multiple mechanisms. While many studies address the functions of animal
coloration, the mechanisms of colour production still remain unknown in
most taxa. Here we compare reflectance spectra, cellular, ultra- and
nano-structure of colour-producing elements, and pigment types in two
freshwater turtles with contrasting courtship behaviour, Trachemys scripta
and Pseudemys concinna. The two species differ in the distribution of
pigment cell-types and in pigment diversity. We found xanthophores,
melanocytes, abundant iridophores and dermal collagen fibres in stripes of
both species. The yellow chin and forelimb stripes of both P. concinna and
T. scripta contain xanthophores and iridophores, but the post-orbital
regions of the two species differ in cell-type distribution. The yellow
post-orbital region of P. concinna contains both xanthophores and
iridophores, while T. scripta has only xanthophores in the yellow-red
postorbital/zygomatic regions. Moreover, in both species, the xanthophores
colouring the yellow-red skin contain carotenoids, pterins and riboflavin,
but T. scripta has a higher diversity of pigments than P. concinna.
Trachemys s. elegans is sexually dichromatic. Differences in the
distribution of pigment cell types across body regions in the two species
may be related to visual signalling but do not match predictions based on
courtship position. Our results demonstrate that archelosaurs share some
colour production mechanisms with amphibians and lepidosaurs (i.e. vertical
layering/stacking of different pigment cell types and interplay of
carotenoids and pterins), but also employ novel mechanisms (i.e.
nano-organization of dermal collagen) shared with mammals.

===

Enav Vidan,  Maria Novosolov,  Aaron M. Bauer,  Fernando Castro Herrera,
Laurent Chirio, Cristiano de Campos Nogueira,  Tiffany M. Doan,  Amir
Lewin,  Danny Meirte,  Zoltan T. Nagy, Daniel Pincheira‐Donoso,  Oliver
J.S. Tallowin,  Omar Torres Carvajal,  Peter Uetz,  Philipp Wagner,
 Yuezhao Wang,  Jonathan Belmaker  & Shai Meiri (2019)
The global biogeography of lizard functional groups.
Journal of Biogeography (advance online publication)
doi:  https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_jbi.13667&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=a8vtKAQkwnqDGbwt0VQVjL76tBJFJ-jok9r3bnZtjI4&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_jbi.13667&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=OLkMolyIJFEdNSTF9KbVkE6qmYS-rYsT0A0K7y1s_jg&e= 

Aim

Understanding the mechanisms determining species richness is a primary goal
of biogeography. Richness patterns of sub‐groups within a taxon are usually
assumed to be driven by similar processes. However, if richness of distinct
ecological strategies respond differently to the same processes, inferences
made for an entire taxon may be misleading. We deconstruct the global
lizard assemblage into functional groups and examine the congruence among
richness patterns between them. We further examine the species richness –
functional richness relationship to elucidate the way functional diversity
contributes to the overall species richness patterns.

Location

Global.

Methods

Using comprehensive biological trait databases we classified the global
lizard assemblage into ecological strategies based on body size, diet,
activity times and microhabitat preferences, using Archetypal Analysis. We
then examined spatial gradients in the richness of each strategy at the
one‐degree grid cell, biome, and realm scales.

Results
We found that lizards can best be characterized by seven “ecological
strategies”: scansorial, terrestrial, nocturnal, herbivorous, fossorial,
large, and semi‐aquatic. There are large differences among the global
richness patterns of these strategies. While the major richness hotspot for
lizards in general is in Australia, several strategies exhibit highest
richness in the Amazon Basin. Importantly, the global maximum in lizard
species richness is achieved at intermediate values of functional diversity
and increasing functional diversity further result in a slow decline of
species richness.

Main conclusions
The deconstruction of the global lizard assemblage along multiple
ecological axes offers a new way to conceive lizard diversity patterns. It
suggests that local lizard richness mostly increases when species belonging
to particular ecological strategies become hyper‐diverse there, and not
because more ecological types are present in the most species rich
localities. Thus maximum richness and maximum ecological diversity do not
overlap. These results shed light on the global richness pattern of
lizards, and highlight previously unidentified spatial patterns in
understudied functional groups.

======

Free pdf:

Nathalie Feiner & Natalie J. Wood (2019)
Lizards possess the most complete tetrapod Hox gene repertoire despite
pervasive structural changes in Hox clusters.
Evolution & Development 21(4): 218-228
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_ede.12300&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=pS6G0b2Bl_t5MoY_fhC3AYRFEnEt_hEmJn9YD-r6FO8&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_ede.12300&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=Nr-U4BN7Ba4BpzHN5vySYkh38zpksWDbCwoFeU9g8pI&e= 


Hox genes are a remarkable example of conservation in animal development
and their nested expression along the head‐to‐tail axis orchestrates
embryonic patterning. Early in vertebrate history, two duplications led to
the emergence of four Hox clusters (A‐D) and redundancy within paralog
groups has been partially accommodated with gene losses. Here we conduct an
inventory of squamate Hox genes using the genomes of 10 lizard and 7 snake
species. Although the HoxC1 gene has been hypothesized to be lost in the
amniote ancestor, we reveal that it is retained in lizards. In contrast,
all snakes lack functional HoxC1 and ‐D12 genes. Varying levels of
degradation suggest differences in the process of gene loss between the two
genes. The vertebrate HoxC1 gene is prone to gene loss and its functional
domains are more variable than those of other Hox1 genes. We describe for
the first time the HoxC1 expression patterns in tetrapods. HoxC1 is broadly
expressed during development in the diencephalon, the neural tube, dorsal
root ganglia, and limb buds in two lizard species. Our study emphasizes the
value of revisiting Hox gene repertoires by densely sampling taxonomic
groups and its feasibility owing to growing sequence resources in
evaluating gene repertoires across taxa.

HIGHLIGHTS
Exploration of the genomes of 17 lizard and snake species revealed the
presence of a Hox gene, HoxC1, that has been thought to be lost in the
amniote ancestor. This finding sheds new light on the evolution of Hox gene
repertoires.


===

Michel Laurin, Océane Lapauze & David Marjanović (2019)
What do ossification sequences tell us about the origin of extant
amphibians?bioRxiv 352609 (preprint)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1101_352609&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=lUteysWhsgiOSYJGPE2XekIguVS_4pu5gOVdUOiqIu0&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.biorxiv.org_content_10.1101_352609v2.abstract&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=IAf1lhyx48wD-93R9pS9UOarIJWY2n5-FBVVtTG_gNM&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.biorxiv.org_content_biorxiv_early_2019_07_23_352609.full.pdf&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=oP4D5gP2ith_4HH-xyRtzMXzDjnRxlf0jfT4bJFtZxo&e= 


The controversial origin of extant amphibians has been studied using
several sources of data and methods, including phylogenetic analyses of
morphological data, molecular dating, stratigraphic data, and integration
of ossification sequence data, but a consensus has failed to emerge. We
have compiled five datasets to assess the relative support for six
competing hypotheses about the origin of extant amphibians: a monophyletic
origin among temnospondyls, a monophyletic origin among lepospondyls, a
diphyletic origin among both temnospondyls and lepospondyls, a diphyletic
origin among temnospondyls alone, and two variants of a triphyletic origin,
in which anurans and urodeles come from different temnospondyl taxa while
caecilians come from lepospondyls and are either closer to anurans and
urodeles or to amniotes. Our datasets comprise ossification sequences of up
to 107 terminal taxa and up to eight cranial bones, and up to 65 terminal
taxa and up to seven appendicular bones, respectively. Among extinct taxa,
only two or three temnospondyl can be analyzed simultaneously for cranial
data, but this is not an insuperable problem because each of the six tested
hypotheses implies a different position of temnospondyls and caecilians
relative to other sampled taxa. For appendicular data, more extinct taxa
can be analyzed, including some lepospondyls and the finned tetrapodomorph
Eusthenopteron, in addition to temnospondyls. The data are analyzed through
maximum likelihood, and the AICc (corrected Akaike Information Criterion)
weights of the six hypotheses allow us to assess their relative support. By
an unexpectedly large margin, our analyses of the cranial data support a
monophyletic origin among lepospondyls; a monophyletic origin among
temnospondyls, the current near-consensus, is a distant second. All other
hypotheses are exceedingly unlikely according to our data. Surprisingly,
analysis of the appendicular data supports triphyly of extant amphibians
within a clade that unites lepospondyls and temnospondyls, contrary to all
molecular and recent paleontological phylogenies, but this conclusion is
not very robust.

===

Yuzhi Hu, Gavin C. Young & Jing Lu (2019)
The Upper Devonian tetrapodomorph Gogonasus andrewsae from Western
Australia: reconstruction of the shoulder girdle and opercular series using
X-ray Micro-Computed Tomography.
Palaeoworld (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.palwor.2019.07.008&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=xxXmQNmQ6ZEUr_dW1juHp8rlB2hYjytfP4TTnMApdqI&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_pii_S1871174X19300484&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=_ojsfBDqO6vzHZczMkOQye4sd7AZvu2Y4mzAk9ZTXEQ&s=nPpRoeitQq2ftTV1OAmHdBSp9Weczx9E4mrc4IJ2DS4&e= 


The tetrapodomorph fish, Gogonasus andrewsae is a three dimensionally
well-preserved sarcopterygian from the Gogo Formation (Frasnian, early
Upper Devonian, ~380 million years ago) in Western Australia.
High-resolution X-ray Micro-Computed Tomography and 3D printouts were used
to obtain a digital reconstruction of its shoulder girdle and opercular
series. Our new findings show the opercular series in a close fit against
the upper bones of the shoulder girdle only if the anocleithrum,
supracleithrum and post-temporal are aligned more horizontally than in
previous reconstructions. The lowermost subopercular bone also differs, in
partly covering the clavicle of the shoulder girdle. The ascending process
of the clavicle, and the ventral process of the anocleithrum, do not fit
closely inside the cleithrum, and perhaps functioned for ligamentous
attachment. A rugose area on the anocleithral process is in a similar
relative position to the attachment of a muscle ligament on the shoulder
girdle of various living actinopterygians. Our manipulation of 3D printouts
permits testing of the morphological fit of extremely fragile acid-etched
bones, and indicates a new way to investigate the constructional morphology
of one or more mechanical units of the vertebrate skeleton. It is suggested
that Micro-CT imaging, reconstruction, visualisation and 3D printing
techniques will provide a rigorous new test leading to modification of
previous reconstructions of extinct vertebrates that were based on
graphical methods and 2D imaging.

===



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