Gravity-defying Behaviors: Identifying Models for Protoaves

Geist, Nicholas R.; Feduccia, Alan

doi:10.1093/icb/40.4.664

Cited by 9 publications

(11 citation statements)

References 37 publications

(22 reference statements)

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“…Finally, since feather antecedents are likely to have appeared initially in small, gliding archosaurs from the middle Triassic Period (220 Myr; Fig. 1; Geist and Feduccia 2000;Jones et al 2000, the function of feathers or feather-like integumentary structures in dinosaurs is problematic.…”

Section: Metabolism and Thermoregulation In Amniotes Living And Extinctmentioning

confidence: 99%

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Ruben

Jones²,

Geist³

2003

Physiological and Biochemical Zoology

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In terms of their diversity and longevity, dinosaurs and birds were/are surely among the most successful of terrestrial vertebrates. Unfortunately, interpreting many aspects of the biology of dinosaurs and the earliest of the birds presents formidable challenges because they are known only from fossils. Nevertheless, a variety of attributes of these taxa can be inferred by identification of shared anatomical structures whose presence is causally linked to specialized functions in living reptiles, birds, and mammals. Studies such as these demonstrate that although dinosaurs and early birds were likely to have been homeothermic, the absence of nasal respiratory turbinates in these animals indicates that they were likely to have maintained reptile-like (ectothermic) metabolic rates during periods of rest or routine activity. Nevertheless, given the metabolic capacities of some extant reptiles during periods of elevated activity, early birds were probably capable of powered flight. Similarly, had, for example, theropod dinosaurs possessed aerobic metabolic capacities and habits equivalent to those of some large, modern tropical latitude lizards (e.g., Varanus), they may well have maintained significant home ranges and actively pursued and killed large prey. Additionally, this scenario of active, although ectothermic, theropod dinosaurs seems reinforced by the likely utilization of crocodilian-like, diaphragm breathing in this group. Finally, persistent in vivo burial of their nests and ap-*

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Section: Metabolism and Thermoregulation In Amniotes Living And Extinctmentioning

confidence: 99%

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Ruben

Jones²,

Geist³

2003

Physiological and Biochemical Zoology

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“…(2000) and . Despite being based on a flawed methodology, the suggestion that Caudipteryx might be a flightless bird, and the implications this may have for feather origins, has been taken seriously and is included in a number of recent papers (e. g. Geist & Feduccia 2000, Martin & Czerkas 2000, Zhang & Zhou 2000. In this paper we re-evaluate the position of the centre of gravity in Caudipte~x, and show that its limb proportions argue convincingly against avian limb kinematics.…”

mentioning

confidence: 91%

Limb proportions and avian terrestrial locomotion

Christiansen

Bonde

2002

J Ornithol

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SummaryPhylogenetic systematics unanimously concludes that birds (Archaeopteryx + crownclade Ayes) are a subgroup of the theropod dinosaurs. The discovery of non-avian theropods from China with large pennaceous feathers offers additional support to this relationship and implies further that feathers cannot be used to define birds, as is traditionally advocated. A recent paper proposed that the feathered oviraptorosaur Caudipw~x was in fact a secondarily flightless bird. This was indicated by the anteriorly placed centre of gravity and the subsequent horizontal femoral posture and associated elongation of the lower leg compared to the trunk. A horizontal femoral posture was not present in non-avian theropods and is associated with profound proportional changes, particularly a thicker diameter to resist the increases in bending and torsional moments about the diaphysis. However, double graphic integration analysis of a more accurate model shows that the centre of gravity in Caudipteryx is situated no further anteriorly than in other non-avian theropods. The long limbs of Caudipteryx are not surprising as limb length is related to phylogeny and body size. Primitive non-avian theropods have proportionally shorter limbs at any given size than more advanced forms, and small species have proportionally longer limbs than large species, as in extant mammals. Other theropods are known with proportionally very long limbs. The femoral morphology of Caudipteryx is identical to those of other nonavian theropods, strongly arguing against avian limb kinematics. It is methodologically flawed to substitute functionally inferred characters for phylogenetic analyses.Keywords: Caudipte~x, limb proportions, centre of gravity, femur proportions, phylogeny. Zusammenfassung Gliedmaflenproportionen und terrestrische Lokomotion der V~6gelDie fortgeschritteneren Raubdinosaurier haben eine groge Menge apomorfer Merkmale mit den V6geln (Archaeopte~x und crown-clade Ayes) gemeinsam, und die meisten Analysen sind zu dem Schluss gekommen, dass die V6gel das Schwestertaxon der Dromaeosaurier sind. Vdgel sind deshalb als eine Untergruppe der Dinosaurier, genauer der Raubdinosaurier, zu betrachten.

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“…As this is not the case it is really invalid to cite these characters as being indicative that Caudipteryx was a secondarily flightless bird. Ironically, according to the more traditional, functional and adaptational models of avian origins (Geist & Feduccia 2000, Tarsitano et al. 2000), an approach also favoured by Ruben & Jones (2000), the body proportions of Caudipteryx would effectively rule out its avian status!…”

Section: Resultsmentioning

confidence: 99%

“…Subsequently, with the advance of cladistic methods, all phylogenetic analyses have unanimously concluded that extant birds are a subgroup of the theropod dinosaurs, most often the sister taxon to the Dromaeosauridae (e. g. Gauthier 1986, Chiappe 1995, Dingus & Rowe 1998, Holtz 1994a, 1998, 2000, Makovicky & Sues 1998, Padian & Chiappe 1998, Sereno 1999). A minority of scientists, however, continue to advocate that birds are unrelated to theropod dinosaurs (e. g. Tarsitano & Hecht 1980, Feduccia 1985, 1996, Martin 1991, Feduccia & Wild 1993, Feduccia & Martin 1996, Geist & Feduccia 2000, Ruben & Jones 2000, Martin & Czerkas 2000; see also Gibbons (1998)). …”

Section: Introductionmentioning

confidence: 99%

“…(2000) and Ruben & Jones (2000) . Despite being based on a flawed methodology, the suggestion that Caudipteryx might be a flightless bird, and the implications this may have for feather origins, has been taken seriously and is included in a number of recent papers (e. g. Geist & Feduccia 2000 , Martin & Czerkas 2000 , Ruben & Jones 2000 , Zhang & Zhou 2000) . In this paper we re‐evaluate the position of the centre of gravity in Caudipteryx , and show that its limb proportions argue convincingly against avian limb kinematics.…”

Section: Introductionmentioning

confidence: 99%

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Limb proportions and avian terrestrial locomotion

Christiansen

Bonde

2002

J Ornithol

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Summary Phylogenetic systematics unanimously concludes that birds (Archaeopteryx + crownclade Aves) are a subgroup of the theropod dinosaurs. The discovery of non‐avian theropods from China with large pennaceous feathers offers additional support to this relationship and implies further that feathers cannot be used to define birds, as is traditionally advocated. A recent paper proposed that the feathered oviraptorosaur Caudipteryx was in fact a secondarily flightless bird. This was indicated by the anteriorly placed centre of gravity and the subsequent horizontal femoral posture and associated elongation of the lower leg compared to the trunk. A horizontal femoral posture was not present in non‐avian theropods and is associated with profound proportional changes, particularly a thicker diameter to resist the increases in bending and torsional moments about the diaphysis. However, double graphic integration analysis of a more accurate model shows that the centre of gravity in Caudipteryx is situated no further anteriorly than in other non‐avian theropods. The long limbs of Caudipteryx are not surprising as limb length is related to phylogeny and body size. Primitive non‐avian theropods have proportionally shorter limbs at any given size than more advanced forms, and small species have proportionally longer limbs than large species, as in extant mammals. Other theropods are known with proportionally very long limbs. The femoral morphology of Caudipteryx is identical to those of other non‐avian theropods, strongly arguing against avian limb kinematics. It is methodologically flawed to substitute functionally inferred characters for phylogenetic analyses.

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Gravity-defying Behaviors: Identifying Models for Protoaves

Cited by 9 publications

References 37 publications

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Limb proportions and avian terrestrial locomotion

Limb proportions and avian terrestrial locomotion

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