Hindlimb myology of the monk parakeet (Aves, Psittaciformes)

Psittaciform birds exhibit novelties in jaw bone structure and musculature that are associated with strong bite forces. These features include an ossified arcus suborbitalis and the muscles ethmomandibularis and pseudomasseter. We analyse the jaw musculature of the monk parakeet (Myiopsitta monachus) to enable future studies aimed at understanding craniofacial development, morphology, function and evolution. We estimate bite force based on muscle dissections, physiological cross‐sectional area and skull biomechanical modelling. We also compare our results with available data for other birds and traced the evolutionary origin of the three novel diagnostic traits. Our results indicate that, in Myiopsitta, (i) the arcus suborbitalis is absent and the orbit is ventrally closed by an elongate processus orbitalis and a short ligamentum suborbitale; (ii) the ethmomandibularis muscle is a conspicuous muscle with two bellies, with its origin on the anterior portion of the septum interorbitale and insertion on the medial aspect of the mandible; (iii) the pseudomasseter muscle consists of some fibers arising from the m. adductor mandibulae externus superficialis, covering the lateral surface of the arcus jugalis and attaches by an aponeurotic sheet on the processus orbitalis; (iv) a well‐developed adductor mandibulae complex is present; (v) the bite force estimation relative to body mass is higher than that calculated for other non‐psittaciform species; and (vi) character evolution analysis revealed that the absence of the arcus suborbitalis and the presence of the m. pseudomassseter are the ancestral conditions, and mapping is inconclusive about presence of one or two bellies of the m. ethmomandibularis.

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“…mps, most parsimony state; *data of the extinct Nandayus vorohuensis obtained from Carril et al. ().…”

Section: Resultsmentioning

confidence: 99%

“…Information on the studied characters was retrieved from the literature (Hofer, , ; Zusi, ; Tokita, , ; Porto, ; Carril et al. ) and from our own observations in Myiopsitta . The tree used is based on the combination of phylogenies of Tavares et al.…”

Section: Methodsmentioning

confidence: 99%

Jaw myology and bite force of the monk parakeet (Aves, Psittaciformes)

2015

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“…Both muscles become well developed by HH36 in quail embryos. Nevertheless, in budgerigar embryos, EBDIV degenerates soon after it separates from the other muscles and is reduced to a thread at HH37 (the presence of a small EBDIV has been reported for one species of parrot [13], but the muscle is absent in other described Psittaciformes [11,26]). On the other hand, the ABDIV becomes strongly developed and its muscle belly extends for four-fifths of the metatarsal length (figure 3a).…”

Section: Results (A) Rotation Of Digit IV In Budgerigar Development (mentioning

confidence: 99%

The developmental origin of zygodactyl feet and its possible loss in the evolution of Passeriformes

et al. 2014

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The zygodactyl orientation of toes (digits II and III pointing forwards, digits I and IV pointing backwards) evolved independently in different extant bird taxa. To understand the origin of this trait in modern birds, we investigated the development of the zygodactyl foot of the budgerigar (Psittaciformes). We compared its muscular development with that of the anisodactyl quail (Galliformes) and show that while the musculus abductor digiti IV (ABDIV) becomes strongly developed at HH36 in both species, the musculus extensor brevis digiti IV (EBDIV) degenerates and almost disappears only in the budgerigar. The asymmetric action of those muscles early in the development of the budgerigar foot causes retroversion of digit IV (dIV). Paralysed budgerigar embryos do not revert dIV and are anisodactyl. Both molecular phylogenetic analysis and palaeontological information suggest that the ancestor of passerines could have been zygodactyl. We followed the development of the zebra finch (Passeriformes) foot muscles and found that in this species, both the primordia of the ABDIV and of the EBDIV fail to develop. These data suggest that loss of asymmetric forces of muscular activity exerted on dIV, caused by the absence of the ABDIV, could have resulted in secondary anisodactyly in Passeriformes.

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“…Arboreal locomotion involves perching, climbing, hanging and moving easily among trees using both the head (jaws, tongue and neck) and hindlimbs (Carril et al. ). All these activities demand a big compromise between visual acuity and gaze stabilization.…”

Section: Discussionmentioning

confidence: 99%

Comparative brain morphology of Neotropical parrots (Aves, Psittaciformes) inferred from virtual 3D endocasts

et al. 2015

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Psittaciformes are a very diverse group of non-passerine birds, with advanced cognitive abilities and highly developed locomotor and feeding behaviours. Using computed tomography and three-dimensional (3D) visualization software, the endocasts of 14 extant Neotropical parrots were reconstructed, with the aim of analysing, comparing and exploring the morphology of the brain within the clade. A 3D geomorphometric analysis was performed, and the encephalization quotient (EQ) was calculated. Brain morphology character states were traced onto a Psittaciformes tree in order to facilitate interpretation of morphological traits in a phylogenetic context. Our results indicate that: (i) there are two conspicuously distinct brain morphologies, one considered walnut type (quadrangular and wider than long) and the other rounded (narrower and rostrally tapered); (ii) Psittaciformes possess a noticeable notch between hemisphaeria that divides the bulbus olfactorius; (iii) the plesiomorphic and most frequently observed characteristics of Neotropical parrots are a rostrally tapered telencephalon in dorsal view, distinctly enlarged dorsal expansion of the eminentia sagittalis and conspicuous fissura mediana; (iv) there is a positive correlation between body mass and brain volume; (v) psittacids are characterized by high EQ values that suggest high brain volumes in relation to their body masses; and (vi) the endocranial morphology of the Psittaciformes as a whole is distinctive relative to other birds. This new knowledge of brain morphology offers much potential for further insight in paleoneurological, phylogenetic and evolutionary studies.

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Hindlimb myology of the monk parakeet (Aves, Psittaciformes)

Cited by 22 publications

References 24 publications

Jaw myology and bite force of the monk parakeet (Aves, Psittaciformes)

Jaw myology and bite force of the monk parakeet (Aves, Psittaciformes)

The developmental origin of zygodactyl feet and its possible loss in the evolution of Passeriformes

Comparative brain morphology of Neotropical parrots (Aves, Psittaciformes) inferred from virtual 3D endocasts

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