Animal Molecular Breeding 2016, Vol.6, No.2, 1-6
2
1.2 Anatomical and paleontological implications
Chromosomal similarities and differences among populations have been reported earlier (
Nyctereutes
procyonoides
and
Nyctereutes procyonoides Ussuriensis
possess 54 chromosomes while
N.p.
Viverinnus
possess
38) (Makinen et al., 1986; Ward et al., 1987), ten homologous autosomes have been recognized while the
remaining chromosomes arms are homologous due to reduction in chromosomal number in Japanese raccoons via
Robertsonian translocations; an occurrence known only in new species evolution (Mayr, 1976).
1.3 The foramen magnum and the contributions of allometry
S
ize, shape and architecture of the foramen magnum differ among species, gender and individuals (De La-hunta,
1983; Rholf, 2010). Foramen magnum index among the subspecies peaks within juveniles’ age group especially in
the smaller subspecies (Zevellof, 2002) though foramen margin morphology remains poorly described, the
occurrence of dorsal notches has not been properly documented in this subject as morphologic variants of
supra-occipital bone ossification differences and not necessarily pathologic (Janeczek et al.
,
2008; Watson
et al.
,
1989) and compatible with longevity more so, they are not associated with any other skull bone deformities except
a degree of directional asymmetry observed in the construction giving rise to behavioral trait (handedness) in
adults (Samuel et al., 2015)*. The most caudo-ventral portion morphology of the occipital condyles also offers
variations which may be of further relevance in classification of the family.
1.4 Anatomical and clinical significance
Occipital index in adulthood in the subspecies of this family differs both from ecologic and subspecies point of
view (Ewer, 1985; Baltrunaite, 2005; Gibson, 2000; Rusbridge and Knowler, 2006; Reid and Helgen, 2008).
Females, in this regard has about 15% attenuated size development of the skull bones (IUCN, 2012). As in other
canids, the possibility of cerebellar protrusion occasioned by volume reduction of the posterior fossa,
syringomyelia and neurological disorders (Rusbridge and Knowler, 2006; Simoens et al.
,
1994) remains potent
with observations of open dorsal notches which Janeczek et al (2008) as reported in dogs (
canis familiaris
) to be
associated with captive breeding and domestication attempts. Variable topographic localization, number and shape
of
condylaris canalis ventralis
observed in different subspecies of genetically related
N.P. cancrivora
as observed
in tropical (Nigerian) subspecies do modify the location of occupant nerves and vessels thereby predisposing to
neuro- vascular accidents (Bartussek, 2004; De Lahunta, 2006), possible causes of such occurrences may be due
to delay in closure of anterior neuropore (Gilbert, 2006) and could be spatial or temporal (Watson et al., 1989;
Gilbert, 2006). This is better studied using computed tomography (Alpak, 2003) compared to the conventional
less reliable methods of analysis (Fike
et al.
,
1984; Jurgelenas et al.
,
2007). This species has not been priory
investigated in environmental and developmental perspectives especially in the tropics, linear cranial
morphometric studies exists in Finland (Kauhala et al.
,
1998), Lithuania (Jurgelenas et al.
,
2007), Russia (Latrov,
1971), Japan (Hidaka et al.
,
1997), Korea (Ellerman and Morrison-Scott, 1951), Germany (Bartussek, 2005;
Zevellof, 2002) and a few other European geographic locations (Ewer, 1985, Helle and Kauhala, 1991, Bartussek,
2004) on similar subject.
2 Materials and Methods
2.1 Literature review
For the purpose of the review, articles were assessed from basic searches from data base of PubMed using terms
like; occipital bone, development, evolution and Nyctereutes procyonoides subspecies. The manuscripts and
books consulted were from 1951 to 2015. Thus the aim of this enquiry was to review literature information on the
occipital bone construction in six known and unreported subspecies of procyonoides skulls from other lands.
Fossil skulls literatures on N.p obtained from prefectures (Bjork, 1973, Hatori et al., 2003; Hohmann et al., 2001)
and museums (Hidaka et al., 1997), those obtained from freshly hunted animals taken from ecologic environments
(Kauhala et al., 1998; Samuel et al., 2015*) and those from Pliocene medieval periods (Hohmann et al., 2001)
were variously consulted for this review.
