The Journal of Basic & Applied Zoology (2013) 66, 145–147

The Egyptian German Society for Zoology

The Journal of Basic & Applied Zoology

www.egsz.orgwww.sciencedirect.com

The origin, the fate and the homology

of the parapolar cartilage of Streptopelia senegalensisaegyptiaca (latham) order columbiformes

Mostafa Zaher *, Azza Riad

Zoology Department-Faculty of Sci., Cairo, Egypt

Received 16 September 2012; revised 22 January 2013; accepted 22 January 2013Available online 3 May 2013

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KEYWORDS

Streptopelia;

Optimum stage;

Trabeculo-polar complex;

Basipterygoid process;

Parapolar cartilage

bbreviations: FEN.SEP.INT

T.CAR., lateral carotid for

ramen; FOR. OPTH., Foram

AR.COM., infracarotid com

INC., incisura optica; P.E

INCOL., processus infrac

andibularis externus; P.MAN

RT., processus retroarticula

.S., planum supraseptale; P

sterior orbital cartilage; PR

POL.C., suprapolar cartilag

mmunis; T.POL.COMX.,

ntral projection of Meckel’s

Corresponding author. Tel.-mail address: dr.mostafaza

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., fenestr

amen; FO

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missure; M

XCOL.,

olumella

.IN., pro

ris; PA

OL. C., p

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trabecu

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Abstract The parapolar cartilage is identified as a cartilaginous nodule with no actual fusion with

the related elements such as the trabeculo-polar complexes and the basipterygoid process. It is in

close proximity to the ventro–lateral border of the hind region of the trabeculo-polar complexes

and on both sides over the basipterygoid process. The parapolar cartilage becomes ossified and

incorporates in the 64 mm nestling stage within the basisphenoid.ª 2013 Production and hosting by Elsevier B.V. on behalf of The Egyptian German Society for Zoology.

a septi interorbitale; FOR.-

R.N.VI., posterior abducens

the ophthalmic artery; INF.-

.C., Meckel’s cartilage; OP-

processus extracolumellaris;

ris; P.MAN.EX., processus

cessus mandibularis internus;

R.POL., parapolar cartilage;

olar cartilage; POS.ORB.C.,

CH., prominentia cochlearis;

., stylohyal; T.C., trabecula

lo-polar complex; V.PROJ.,

05297098.oo.ca (M. Zaher).

Egyptian German Society for

g by Elsevier

ng by Elsevier B.V. on behalf of T

.003

Introduction

The present authors had the opportunity to examine a quitecomplete set of embryos of many species of birds belonging

to four different orders. These orders are Passeriformes, Char-adriiformes, columbiformes and Gruiformes. Among the pecu-liar structures the authors have traced is a cartilaginousnodule, which nominated the parapolar cartilage, found in

the sphenotemporal region of the optimum stage of the chon-drocranium of Streptopelia senegalensis aegyptiaca (Latham);the palm dove, the Egyptian form (order Columbiformes). It

is thus the purpose of this concise article to follow the originand fate of this parapolar element and to attempt itshomology.

Material and method

The material for this investigation implied the necessity of

examining the series of transverse sections of some old em-bryos and a nestling stage of S. senegalensis aegyptiaca. These

he Egyptian German Society for Zoology.

146 M. Zaher, A. Riad

were 39 mm, 45 mm and 53 mm total body length embryos aswell as the 64 mm. total body length nestling stage. These em-bryos and the nestling were chosen from the extensive collec-

tion of embryos and nestlings prepared for the study of thechondrogenesis of this bird (Zaher and Riad, 2009, 2012, inpress-a, in press-b). The sphenotemporal region of the

53 mm. embryo is graphically reconstructed in a lateral view.

Results

The sphenotemporal region of the 53 mm. total body lengthembryo of Streptopelia (=the optimum stage of the chondro-cranium) shows a peculiar structure which has chondrified for

the first time in this embryo, since it is absent in a younger oneof 39 mm total body length. In the 45 mm embryo, its primaryprimordium is laid down. In close proximity to the ventro–lat-

eral border of the hind region of the trabeculo-polar com-plexes, (T.POL.COMX) and on both sides over thebasipterygoid process (P.BASPT.), a cartilaginous nodule isidentified. There is no actual fusion between the nodule and

the related elements. It is of considerable size about 415 mi-crons in length, oval in shape with its long axis obliquely dis-posed to the long axis of the chondrocranium (Fig. 1). This

nodule has thus a separate centre of chondrification quiteapart from the trabeculo-polar complex and the basipterygoidprocess. It is conceivable to nominate this nodule as the para-

polar cartilage due to its close relationship to the trabeculo-po-lar complex (Fig. 1 PAR.POL.). Of interest is the fact that theparapolar nodule becomes ossified and incorporates in the64 mm. nestling stage within the basisphenoid.

Figure 1 Graphic reconstruction of the sphenotemporal region

of the neurocranium of the 53 mm total body length embryo of

Streptopelia senegalensis aegyptiaca (the optimum stage of devel-

opment) in a lateral view. The quadrate cartilage is removed.

Discussion

In the 48.4 mm embryo of Eryx jaculus (a snake from the fam-ily Boidae), Kamal and Hammouda (1965) recognized a small

cartilaginous rod-shaped basitrabecular process jutting fromthe dorso–lateral border of the posterior part of each trabeculacranii in front of the anterior margin of the parachordal plate.

Its free blunt end is directed anteriorly, while posteriorly itfuses completely without any sign of demarcation with the tra-becula. It has thus no separate centre of chondrification. In the92.2 mm embryo of the same species, the basitrabecular pro-

cess becomes detached from the trabecula cranii. Brock(1941) observed the same structure in Python (also a snakefrom the family Boidae) which behaves identically similar to

that of Eryx. Brock (1941) and Kamal and Hammouda(1965) discussed thoroughly the basitrabecular question andon account of its topographic position in relation to the hind

region of the trabecula, they concluded that the basitrabecularelement in Ophidia is homologous with the basitrabecular nod-ule commonly found in Lacertilia. Its detachment from the tra-

becula is a secondary character. Thus the presence of thebasitrabecular element is actually a primitive affinity and oftrue phylogenetic value.

Undoubtedly, the parapolar cartilage of Streptopelia is lo-

cated in a, more or less, corresponding position as found inthe majority of lacertilian forms (e.g. Lacerta; Gaupp, 1900and De Beer, 1930; Eumeces; Rice, 1920; Lygosoma; Pearson,

1921; Calotes; Ramaswami, 1946; Chalcides; El-Toubi andKamal, 1959a,b). In crocodiles, De Beer (1937) recorded thepresence of a basitrabecular process from which an infrapolar

process comes out underlying the anterior portion of the par-achordal plate. It is not improbable that the parapolar noduleof Streptopelia shows a straight homology to the basitrabecu-

lar element of the lacertilian forms beyond the fact that inStreptopelia it has a separate centre of chondrification. Itspresence in Streptopelia could be considered as a primitive lac-ertilian character. As far as the author is aware, the parapolar

nodule described in the present study has never been met within the avian literature.

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