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Gross Anatomy of the Splanchnocranium in the Great Indian Horned Owl (Bubo Bengalensis)

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Gross Anatomy of the Splanchnocranium in the Great Indian Horned Owl (Bubo Bengalensis) Int.J.Curr.Microbiol.App.Sci (2020) 9(3): 1873-1878 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 9 Number 3 (2020) Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2020.903.217 Gross Anatomy of the Splanchnocranium in the Great Indian Horned Owl (Bubo bengalensis) K. Rajalakshmi*, P. Sridevi and M. Siva Kumar Department of Veterinary Anatomy and Histology, Rajiv Gandhi Institute of Veterinary Education and Research, Kurumbapet, Puducherry-605010, India *Corresponding author ABSTRACT A study was conducted on the gross features of the splanchnocranium of an aged great Indian horned owl and its morphological peculiarities were K e yw or ds correlated with its possible functions. The horizontal plate of ethmoid was Premaxilla, wide and well developed. The lacrimal was very large and the lower Maxilla, orbital ring was incomplete. The external nares were oval in shape. The Pterygoid, premaxilla was steeply curved down and had a hooked tip. The maxilla Lacrimal was highly reduced and formed a movable articulation with the palatine and Article Info zygomatic bone. The rod like zygomaticus formed a movable articulation Accepted: rostrally with the maxilla and caudally with quadrate. The paired palatines 12 February 2020 were horizontal in position and formed the strong bone of the upper jaw. Available Online: The pterygoid was a thin short and which articulated cranially with 10 March 2020 palatine, behind with parasphenoid process of presphenoid and caudally with quadrate. The quadrate was semi-circular. Introduction the birds of prey. The temporal and anti- orbital fenestrae in both paleognaths and The splanchnocranium (bones of the face) is neognaths have merged with the orbit clearly demarcated from the neurocranium by (Knutsen, 2007). An important feature of the orbital cavities. The size of birds is cranial kinesis which is the movement splanchnocranium is largely dependent on the of the upper jaw in relation to the brain case. diet and feeding habits of the bird (Nickel et It is generated by a complex mechanism in al., 1986). The birds rostrum is composed of the skull. Since the quadrate bone articulates teeth less jaws covered by a honey sheath, with the brain case, pterygoid bones, jugal known as the ramphotheca. Birds jaws are arches and mandible are pivoting points in powerful tools used for feeding, especially in cranial kinesis. The Indian eagle-owl also 1873 Int.J.Curr.Microbiol.App.Sci (2020) 9(3): 1873-1878 called the rock eagle owl or Bengal eagle-owl the paired olfactory foramen for the passage is a species of large horned owl restricted to of olfactory nerves into the nasal cavity. The the Indian subcontinent. Their diet through thick perpendicular plate of ethmoid formed much of the year consists of rodents, when the interorbital septum along with the orbital feeding on rodents, they tear up the prey, plates of frontal joined the nasal septum rather than swallow them whole. This large rostrally. A similar observation was reported owl with distinctive face, large forward- by Indu et al., 2013 in green-winged macaw. facing eyes, horns and deep resonant call is However in domestic fowl and Japanese associated with a number of superstitions. quails, the ethmoid was thin and small and Gross morphological studies on the skull of formed the cranio-dorsal wall of the orbit and domestic fowl, pigeon and goose have been the olfactory foramen was located in the discussed in various text books of Anatomy dorsomedial part of the perpendicular plate (Nickel et al., 1986). However, not much (Fitzgerald, 1969, Nickel et al., 1986). John information is available on the skull of owl. et al., 2016 in crow reported that the Hence the present study was undertaken to horizontal part was reduced. The wide investigate the morphological variations in the horizontal plate of ethmoid in owl could be a splanchnocranium and to correlate it with means of adaptation to accommodate the well their possible functions. developed nasal, lacrimal and premaxilla. Moreover it also formed the strong posterior Materials and Methods base of the cranio-facial hinge. The materials for the study were collected The interobital septum was pierced by the from owl brought for post mortem interorbital septal notch which was located examination to the Department of Veterinary rostrally and below the olfactory foramen. Pathology Rajiv Gandhi Institute of The optic foramen was smaller and was Veterinary Education and Research, smaller and was placed far behind the Puducherry. The bones were removed and interorbital septal notch. John et al., 2016 collected by the regular process of mentioned that the optic foramen was located maceration, cleaned, dried and the various adjacent to the caudal boundary of the notch gross anatomical features were recorded. in crow. Results and Discussion Lacrimal The bones of the splachnocranium comprised The lacrimal was very large and was fused of the lacrimal, nasal, premaxilla, maxilla, with the frontal bone behind and formed a zygomatic, palatine, Pterygoid, vomer, movable articulation with the nasal bone in quadrate and mandible. The ethmoid was front called as cranio-facial hinge. It shared by both neurocranium and consisted of two lacrimal process dorsal and splachnocranium (Nickel et al., 1986). ventral. The dorsal lacrimal process (Fig.1) was short triangular in outline and its apex The ethmoid consisted of two parts namely faced towards the orbit. Whereas Indu et al., the horizontal and perpendicular plate. The 2013 observed a caudo-ventrally directed horizontal plate was located craniodorsally lacrimal process in green-winged macaw. and formed the anterior wall of the orbit of Moreover, in duck, fowl and Japanese quail, separated the orbit from the nasal cavity. It the lacrimal process was absent and the was wide well developed in the owl and had ventral wall of the orbit was incomplete 1874 Int.J.Curr.Microbiol.App.Sci (2020) 9(3): 1873-1878 (Fitzgerald, 1969 and Nickel et al., 1986). Premaxilla The ventral lacrimal process was an elongate flattered bony plate. John et al., 2016 also The paired premaxilla formed the largest part noticed a well developed ventrally directed of the upper jaw and was covered by the lacrimal process in crow. It was caudally or horny beak. It had a body and three caudo ventrally directed and faced the orbital processes, the frontal, palatine and maxillary process of quadrate being separated from it by process as reported by Nickel et al., 1977 in a considerable space. Hence, an incomplete domestic fowl and Indu et al., 2013 in green- lower orbital ring was noticed. However, Indu winged macaw. Maxillary process supported et al., 2013 in green-winged macaw stated part of the beak and was fused with the that the caudo-ventrally directed lacrimal maxilla. Palatine process was very large and process fused with the orbital process of spongy and united with each other and with temporal and formed a small nearly circular the ossified nasal septum and occupied the complete lower orbital ring. entire base of the beak. However, Nickel et al., 1986 in fowl reported that the palatine Nasal processes were very narrow with a broad cleft in between them. The frontal process were Nasal bones formed a part of the upper beak medially fused and reached up to the frontal and a greater part of the roof of the nasal bone. The maxillary and intermaxillary cavity. It comprised of three well developed process of nasal bone was fused with the processes namely the frontal, maxillary and frontal and maxillary process of premaxilla. intermaxillary process. A similar observation (Fig.2). was reported by Nickel et al., 1977 in domestic fowl. The frontal process of nasal Maxilla was fused with the nasal part of the frontal bone. The dorsal face of the frontal process The maxilla was highly reduced and formed of the nasal bone presented the infra orbital the caudal boundary of the upper beak. John foramen. The intermaxillary process of nasal et al., 2016 had also reported a highly reduced bone formed the dorsal boundary of the maxilla in the crow. It was fused with the external nares. The maxillary process formed nasal and premaxilla. It had two processes, the lower boundary of the external nares. the palatine and zygomatic which formed According to John et al., 2016, in crow, the movable articulations with the palatine and lateral process of nasal bone formed the zygomatic bones respectively. aboral and lower borders of the nares. The external nares or operculum was oval in shape Zygomatic in owl. The zygomatic was rod like and formed The nostrils were positioned towards the base movable articulations with the maxilla of the beak, in a region called the cere. A rostrally and quadrate caudally. The well-developed naso frontal hinge or cranio maxillary portion of zygomatic appeared facial hinge was formed due to the flattened and was inserted to the posterior articulation between frontal process of nasal edge of the beak which was at a higher place bone with the cranial border of the frontal. A than the insertion of palatine bones. These similar observation was reported in crow by observations were in accordance with the John et al., 2016. findings of Indu et al., 2013, in green-winged macaw. However, Patki et al., 2009 in fowl, 1875 Int.J.Curr.Microbiol.App.Sci (2020) 9(3): 1873-1878 turkey, guinea fowl and crow reported that the shaped cranially and plate like caudally. zygomatic bones were thin, rod-like Contrarily, John et al., (2016) mentioned that elongation of the rim of the upper back. palatine bone was roughly triangular at its proximal end and rod shaped towards the Palatine distal end. Nickel et al., (1977) reported that the palatine rod bone was shaped in fowl and The paired palatine bones were horizontal in pigeon while in duck and goose they were in position and formed a strong bone of the the form of bony plates.
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