Combining Shape Data and Traditional Measurements with the 2B-PLS: Testing the Covariation Between Avian Brain Size and Cranial Shape Variation as an Example

The impact of allometry on vomer shape and its implications for the taxonomy and cranial kinesis of crown-group birds

10.1101/2020.07.02.184101 ◽

2020 ◽

Author(s):

Olivia Plateau ◽

Christian Foth

Keyword(s):

Anterior Part ◽

Correct Identification ◽

Temporal Region ◽

Shape Variation ◽

Crown Group ◽

Multivariate Statistical ◽

Morphological Differences ◽

Cranial Kinesis ◽

The Impact ◽

Shape Data

AbstractCrown birds are subdivided into two main groups, Palaeognathae and Neognathae, that can be distinguished, among others, by the organization of the bones in their pterygoid-palatine complex (PPC). Shape variation to the vomer, which is the most anterior part of the PPC, was recently analysed by Hu et al. (2019) with help of geometric morphometrics to discover morphological differences between palaeognath and neognath birds. Based on this study, the vomer was identified as sufficient to distinguish the two main groups (and even more inclusive neognath groups) and their cranial kinetic system. As there are notable size differences between the skulls of palaeognaths and neognaths, we here investigate the impact of allometry on vomeral shape and its implication for taxonomic classification by re-analysing the data of the previous study. Different types of multivariate statistical analyses reveal that taxonomic identification based on vomeral shape is strongly impaired by allometry, as the error of correct identification is high when shape data is corrected for size. This finding is evident by a great overlap between palaeognath and neognath subclades in morphospace. The correct identification is further influenced by the convergent presence of a flattened vomeral morphotype in multiple neognath subclades. As the evolution of cranial kinesis has been linked to vomeral shape in the original study, the existing correlation between shape and size of the vomer across different bird groups found in the present study questions this conclusion. In fact, cranial kinesis in crown birds results from the loss of the jugal-postorbital bar in the temporal region and ectopterygoid in the PPC and the combination of a mobilized quadrate-zygomatic arch complex and a flexible PPC. Therefore, we can conclude that the vomer itself is not a suitable proxy for exploring the evolution of cranial kinesis in crown birds and their ancestors.

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The taxonomic implications of cranial shape variation in Homo erectus

Journal of Human Evolution ◽

10.1016/j.jhevol.2007.11.003 ◽

2008 ◽

Vol 54 (6) ◽

pp. 827-847 ◽

Cited By ~ 75

Author(s):

Karen L. Baab

Keyword(s):

Homo Erectus ◽

Shape Variation ◽

Taxonomic Implications ◽

Cranial Shape

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Combining deep learning with 3D stereophotogrammetry for craniosynostosis diagnosis

Scientific Reports ◽

10.1038/s41598-020-72143-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Guido de Jong ◽

Elmar Bijlsma ◽

Jene Meulstee ◽

Myrte Wennen ◽

Erik van Lindert ◽

...

Keyword(s):

Deep Learning ◽

Learning Algorithm ◽

Normal Brain ◽

Healthy Controls ◽

Learning Network ◽

Deep Learning Algorithm ◽

Anterior Plagiocephaly ◽

Deep Learning Network ◽

Shape Data ◽

Cranial Shape

Abstract Craniosynostosis is a condition in which cranial sutures fuse prematurely, causing problems in normal brain and skull growth in infants. To limit the extent of cosmetic and functional problems, swift diagnosis is needed. The goal of this study is to investigate if a deep learning algorithm is capable of correctly classifying the head shape of infants as either healthy controls, or as one of the following three craniosynostosis subtypes; scaphocephaly, trigonocephaly or anterior plagiocephaly. In order to acquire cranial shape data, 3D stereophotographs were made during routine pre-operative appointments of scaphocephaly (n = 76), trigonocephaly (n = 40) and anterior plagiocephaly (n = 27) patients. 3D Stereophotographs of healthy infants (n = 53) were made between the age of 3–6 months. The cranial shape data was sampled and a deep learning network was used to classify the cranial shape data as either: healthy control, scaphocephaly patient, trigonocephaly patient or anterior plagiocephaly patient. For the training and testing of the deep learning network, a stratified tenfold cross validation was used. During testing 195 out of 196 3D stereophotographs (99.5%) were correctly classified. This study shows that trained deep learning algorithms, based on 3D stereophotographs, can discriminate between craniosynostosis subtypes and healthy controls with high accuracy.

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Heterochronic Shifts Mediate Ecomorphological Convergence in Skull Shape of Microcephalic Sea Snakes

Integrative and Comparative Biology ◽

10.1093/icb/icz033 ◽

2019 ◽

Vol 59 (3) ◽

pp. 616-624 ◽

Cited By ~ 9

Author(s):

Emma Sherratt ◽

Kate L Sanders ◽

Amy Watson ◽

Mark N Hutchinson ◽

Michael S Y Lee ◽

...

Keyword(s):

Morphological Changes ◽

Shape Variation ◽

Micro Computed Tomography ◽

Trophic Specialization ◽

Evolutionary Patterns ◽

Dietary Specialization ◽

Geometric Morphometric ◽

Sea Snakes ◽

Morphometric Methods ◽

Cranial Shape

Abstract Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.

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A three-dimensional geometric morphometrics view of the cranial shape variation and population history in the New World

American Journal of Human Biology ◽

10.1002/ajhb.22845 ◽

2016 ◽

Vol 28 (5) ◽

pp. 646-661 ◽

Cited By ~ 16

Author(s):

Manon Galland ◽

Martin Friess

Keyword(s):

Geometric Morphometrics ◽

New World ◽

Three Dimensional ◽

Population History ◽

Shape Variation ◽

Cranial Shape

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Initial Investigations of the Cranial Size and Shape of Adult Eurasian Otters (Lutra lutra) in Great Britain

10.20944/preprints202007.0195.v1 ◽

2020 ◽

Author(s):

Damian JJ Farnell ◽

Chern Khor ◽

Zoe Doyle ◽

Wayne N Ayre ◽

Elizabeth Chadwick

Keyword(s):

Great Britain ◽

Geographical Area ◽

Cranial Morphology ◽

Lutra Lutra ◽

Shape Variation ◽

Distance Measurements ◽

Size And Shape ◽

Physical Measurements ◽

3D Surface ◽

Shape Data

3D surface scans were carried out to determine the shapes of the upper sections of (skeletal) crania of adult Eurasian otters (Lutra lutra) from Great Britain. Landmark points were placed on these shapes by using a graphical user interface (GUI) and distance measurements (i.e., the length, height, and width of the crania) could be found by using the landmark points. These “GUI-based” distances were shown to be accurate and reliable in comparison to physical measurements taken on the crania directly by using a digital calliper. The crania of males were 6.85mm, 5.44mm, 1.66mm larger in terms of length, width and height, respectively, than females in our sample (P < 0.001), i.e., male otters had significantly larger skulls than females. Significant differences in size occurred also by geographical area in Great Britain (P < 0.05). Multilevel Principal Components Analysis (mPCA) indicated that sex and geographical area explained 31.1% and 9.6% of shape variation in “unscaled” shape data and that they explained 17.2% and 9.7% of variation in “scaled” data. The first mode of variation at level 1 (sex) correctly reflected size changes between males and females for “unscaled” shape data. Modes at level 2 (geographical area) also showed possible changes in size and shape. Clustering by sex and geographical area was observed in standardised component scores. Such clustering in cranial shape by geographical area might reflect genetic differences that are known to occur in otter populations in Great Britain, although other potentially confounding factors (e.g. population age-structure, diet, etc.) might also drive regional differences. Furthermore, sample sizes per group were small for geographical comparisons. However, this work provides a successful first test of the effectiveness of 3D surface scans and multivariate methods such as mPCA to study the cranial morphology of otters.

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Evolutionary morphology of the rabbit skull

PeerJ ◽

10.7717/peerj.2453 ◽

2016 ◽

Vol 4 ◽

pp. e2453 ◽

Cited By ~ 5

Author(s):

Brian Kraatz ◽

Emma Sherratt

Keyword(s):

Small Proportion ◽

Phylogenetic Signal ◽

Morphological Data ◽

Shape Variation ◽

Evolutionary Morphology ◽

Crown Group ◽

Size Change ◽

Generalist Species ◽

Facial Region ◽

Cranial Shape

The skull of leporids (rabbits and hares) is highly transformed, typified by pronounced arching of the dorsal skull and ventral flexion of the facial region (i.e., facial tilt). Previous studies show that locomotor behavior influences aspects of cranial shape in leporids, and here we use an extensive 3D geometric morphometrics dataset to further explore what influences leporid cranial diversity. Facial tilt angle, a trait that strongly correlates with locomotor mode, significantly predicts the cranial shape variation captured by the primary axis of cranial shape space, and describes a small proportion (13.2%) of overall cranial shape variation in the clade. However, locomotor mode does not correlate with overall cranial shape variation in the clade, because there are two district morphologies of generalist species, and saltators and cursorial species have similar morphologies. Cranial shape changes due to phyletic size change (evolutionary allometry) also describes a small proportion (12.5%) of cranial shape variation in the clade, but this is largely driven by the smallest living leporid, the pygmy rabbit (Brachylagus idahoensis). By integrating phylogenetic history with our geometric morphometric data, we show that the leporid cranium exhibits weak phylogenetic signal and substantial homoplasy. Though these results make it difficult to reconstruct what the ‘ancestral’ leporid skull looked like, the fossil records suggest that dorsal arching and facial tilt could have occurred before the origin of the crown group. Lastly, our study highlights the diversity of cranial variation in crown leporids, and highlights a need for additional phylogenetic work that includes stem (fossil) leporids and includes morphological data that captures the transformed morphology of rabbits and hares.

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