Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling

Hone, David W. E.; Wood, D M; Knell, Robert J.

doi:10.26879/591

Cited by 17 publications

(30 citation statements)

References 48 publications

(77 reference statements)

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“…As one of the first quantitative studies of ceratopsian cranial shape, we found substantial support for heterochronic processes in the evolution of the hallmark parieto‐squamosal frill that diagnoses the clade. Acceleration is the main mechanism that accounts for the macroevolutionary shift in frill shape and size between the LCA of Neoceratopsia with a short, narrow frill throughout ontogeny, and coronosaurs, which have significantly longer and wider frills in adults (Hone et al., 2016). Furthermore, shifts in Regression Scores correlated with shifts in centroid size between early‐diverging coronosaurs and the Triceratops ontogenetic vector are broadly consistent with a peramorphocline between early‐diverging coronosaurs and ceratopsids as suggested by Long and McNamara (1995), although the exact details differ.…”

Section: Discussionmentioning

confidence: 99%

“…Current reconstructions of jaw muscles in these animals place the jaw adductor origins closer to the rostral edge of the supratemporal fenestra, along the midline keel of the frill, and along the inner surface of the squamosal, with the majority of the frill, including its caudal margin, free of musculature (Dodson, 1996; Nabavizadeh, 2018). These differences in frill anatomy between early and late diverging ceratopsians prompted Makovicky (2012) and Makovicky and Norell (2006) to propose that the ceratopsian frill underwent a shift in its primary function within Neoceratopsia from providing an increased area for attachment of jaw adductor muscles as (Haas, 1955; Lull, 1908; Ostrom, 1964; Xu et al., 2002), to serving as a species‐specific display structure with possible social and/or sexual functions (Dodson, 1976, 1993, 1996; Farlow & Dodson, 1975; Hone, Naish, & Cuthill, 2012; Hone et al., 2016; Horner & Goodwin, 2006, 2008; O'Brien et al., 2018; Padian & Horner, 2011; Sampson, Ryan, & Tanke, 1997). Insertion of jaw musculature along the majority of the frill margin in early‐diverging taxa such as Liaoceratops , Yamaceratops (Makovicky & Norell, 2006), and Auroraceratops (Morshhauser et al, 2019) would likely have constrained allometric growth patterns by optimizing muscle orientations and mechanical leverage, a conclusion supported by the observed absence of ontogenetic shape change in Liaoceratops and the LCA of Neoceratopsia (Figure 7a).…”

Section: Discussionmentioning

confidence: 99%

“…Only five exemplars of L. yanzigouensis were available, but these spanned a substantial range of sizes (Table 2). P. andrewsi is known from numerous specimens, many of which are exceptionally preserved, including a nearly complete developmental series ranging from hatchlings through full‐grown adults (Brown & Schlaikjer, 1940; Dodson, 1976; Fastovsky et al., 2011; Hone, Wood, & Knell, 2016; Lull, 1908; Russell, 1935). The growth series of 21 P. andrewsi and the nine specimens of the new Ukhaa Tolgod protoceratopsid spanned much of the development of these species, with specimens ranging from a few dozens of mm to more than 300 mm in basal skull length (Table 2).…”

Section: Methodsmentioning

confidence: 99%

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Modularity and heterochrony in the evolution of the ceratopsian dinosaur frill

Prieto-Márquez

Garcia‐Porta

Joshi

et al. 2020

Ecology and Evolution

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The fossil record provides compelling examples of heterochrony at macroevolutionary scales such as the peramorphic giant antlers of the Irish elk. Heterochrony has also been invoked in the evolution of the distinctive cranial frill of ceratopsian dinosaurs such as Triceratops. Although ceratopsian frills vary in size, shape, and ornamentation, quantitative analyses that would allow for testing hypotheses of heterochrony are lacking. Here, we use geometric morphometrics to examine frill shape variation across ceratopsian diversity and within four species preserving growth series. We then test whether the frill constitutes an evolvable module both across and within species, and compare growth trajectories of taxa with ontogenetic growth series to identify heterochronic processes. Evolution of the ceratopsian frill consisted primarily of progressive expansion of its caudal and caudolateral margins, with morphospace occupation following taxonomic groups. Although taphonomic distortion represents a complicating factor, our data support modularity both across and within species. Peramorphosis played an important role in frill evolution, with acceleration operating early in neoceratopsian evolution followed by progenesis in later diverging cornosaurian ceratopsians. Peramorphic evolution of the ceratopsian frill may have been facilitated by the decoupling of this structure from the jaw musculature, an inference that predicts an expansion of morphospace occupation and higher evolutionary rates among ceratopsids as indeed borne out by our data. However, denser sampling of the meager record of early‐diverging taxa is required to test this further.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Modularity and heterochrony in the evolution of the ceratopsian dinosaur frill

Prieto-Márquez

Garcia‐Porta

Joshi

et al. 2020

Ecology and Evolution

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“…The functions of these are still debated, including aposematism, anti-glare, dazzle, conspecific signaling, and thermoregulation [ 37 ]. It is worth noting that the jugal bosses in ceratopsians have been suggested to have had a signaling function [ 38 ]. We note that the heavy pigmentation in the face is not locked into scales and could thus have been involved in a more colorful display through chromatophores also.…”

Section: Discussionmentioning

confidence: 99%

3D Camouflage in an Ornithischian Dinosaur

Nicholls²,

et al. 2016

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SummaryCountershading was one of the first proposed mechanisms of camouflage [1, 2]. A dark dorsum and light ventrum counteract the gradient created by illumination from above, obliterating cues to 3D shape [3, 4, 5, 6]. Because the optimal countershading varies strongly with light environment [7, 8, 9], pigmentation patterns give clues to an animal’s habitat. Indeed, comparative evidence from ungulates [9] shows that interspecific variation in countershading matches predictions: in open habitats, where direct overhead sunshine dominates, a sharp dark-light color transition high up the body is evident; in closed habitats (e.g., under forest canopy), diffuse illumination dominates and a smoother dorsoventral gradation is found. We can apply this approach to extinct animals in which the preservation of fossil melanin allows reconstruction of coloration [10, 11, 12, 13, 14, 15]. Here we present a study of an exceptionally well-preserved specimen of Psittacosaurus sp. from the Chinese Jehol biota [16, 17]. This Psittacosaurus was countershaded [16] with a light underbelly and tail, whereas the chest was more pigmented. Other patterns resemble disruptive camouflage, whereas the chin and jugal bosses on the face appear dark. We projected the color patterns onto an anatomically accurate life-size model in order to assess their function experimentally. The patterns are compared to the predicted optimal countershading from the measured radiance patterns generated on an identical uniform gray model in direct versus diffuse illumination. These studies suggest that Psittacosaurus sp. inhabited a closed habitat such as a forest with a relatively dense canopy.Video Abstract

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“…) and this has been demonstrated for some dinosaur species (Dodson , ; Evans ; Hone et al . ). However, ongoing increases in the size of a structure, or a change in morphology (such as body size), over many years may add to the problem of a (non‐binary) continuum of features in dinosaurs.…”

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confidence: 97%

Protracted growth impedes the detection of sexual dimorphism in non‐avian dinosaurs

Hone

Mallon

2017

Palaeontology

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Evidence for sexual dimorphism is extremely limited in the non‐avian dinosaurs despite their high diversity and disparity, and despite the fact that dimorphism is very common in vertebrate lineages of all kinds. Using body‐size data from both Alligator mississippiensis and Rhea americana, which phylogenetically bracket the dinosaurs, we demonstrate that even when there is strong dimorphism in a species, random sampling of populations of individuals characterized by sustained periods of growth (as in the alligator and most dinosaurs) can result in the loss of this signal. Dimorphism may be common in fossil taxa but very hard to detect without ontogenetic age control and large sample sizes, both of which are hampered by the limitations of the fossil record. Signal detection may be further hindered by Type III survivorship, whereby increased mortality among the young favours the likelihood that they will be sampled (unless predation or taphonomic bias against small size acts against this). These, and other considerations relating to behaviour and ecology, provide powerful reasons to suggest that sexual dimorphism in dinosaurs may be very difficult to detect in almost all currently available samples. Similar issues are likely also to be applicable to many fossil reptiles, or animals more generally.

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Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling

Cited by 17 publications

References 48 publications

Modularity and heterochrony in the evolution of the ceratopsian dinosaur frill

Modularity and heterochrony in the evolution of the ceratopsian dinosaur frill

3D Camouflage in an Ornithischian Dinosaur

Protracted growth impedes the detection of sexual dimorphism in non‐avian dinosaurs

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