New Fossil Remains of Giraffids from the Lower Siwaliks of Punjab, Pakistan: Evolution, Systematics and Biogeography

Amin Arif1, Khizar Samiullah1*, Riffat Yasin2, Bilal Rasool1, Shakila Naz1, Xijun Ni3 and Saleem Akhtar1

1Department of Zoology, GC University, Faisalabad, Pakistan

2Faculty of Veterinary and Animal Sciences, Muhammad Nawaz Sharif University of Agriculture, Multan, Punjab, Pakistan

3Institute of Vertebrate Palaeontology and Palaeoanthropology, Beijing, China

ABSTRACT

Taxonomic study from a late Miocene Fossil locality Dhok Bun Ameer Khatoon, Lower Siwalik Hills of Pakistan has been conducted. New fossil remains belong to family Giraffidae which include right and left maxilla, isolated upper premolars and molars. After morphological and comparative analysis, the collection is attributed to Giraffokeryx punjabiensis and Giraffa priscilla. Size variation in dentition is taxonomically important for vertebrate evolutionary point of view and this is the main reason to conduct this study at this specific site to add additional information about family Giraffidae. The fossil site has well exposed Chinji and Nagri Formation and has dated approximately 14.2-9.5 Ma. In this study, different aspects of evolution, taxonomy and biogeographic distribution as well as the relation of Giraffidae with Procerotidae have been discussed comprehensively. Palaeoenvironment, biostratigraphy and geology of the locality have also been discussed. The coexistence of Giraffokeryx punjabiens with its mammalian paleo-community reveals the persistence of mosaics of diverse habitats ranging from tropical evergreen forest to subtropical ones, closed seasonal woodlands to wooded savannas during the deposition of the Dhok Bun Ameer Khatoon, Chinji Formation.

Article Information

Received 05 August 2018

Revised 29 May 2019

Accepted 05 November 2020

Available online 09 February 2021

(early access)

Published 03 December 2021

Authors’ Contribution

KS, RY and XN presented the concept and designed the study. AA, SA and SN helped in collection and preparation of fossils. KS and BR drafted the manuscript.

Key words

Miocene, Giraffidae, Lower siwaliks, Chinji formation

DOI: https://dx.doi.org/10.17582/journal.pjz/20180805150835

* Corresponding author: [email protected]

0030-9923/2022/0001-0265 $ 9.00/0

Copyright 2022 Zoological Society of Pakistan

INTRODUCTION

The Siwalik Group, in the northern part of the Subcontinent, consists of thick sequence of terrestrial deposits which shows a relatively high degree of completeness over most of the Neogene’s time (Flynn et al., 1995; Flynn, 2003). The molasse-type sediments of Neogene and that of early Quaternary age occupied the forland basin of Siwaliks which is developed at the foothills of Himalayan mountain belt. The continental sedimentation as well as complete record of vertebrate fauna especially mammals is well preserved in the stratigraphic sequence of Siwaliks (Basu, 2004).

Dhok Bun Ameer Khatoon is a small village located about 16 Km from Chua Seydon Shah (North-East) in Chakwal district, Punjab, Pakistan. This locality (32o 47’ 26.4” N, 72° 55’ 35.7” E) mainly composed of Miocene deposits of Lower Siwaliks. Rich fossil fauna of vertebrate alongwith unique colored shale containing unweathered igneous minerals and notable amount of feldspar is a characteristic of this locality. This area, in the southern Potwar Plateau, has exposed the most complete sequence of Siwalik group. The stratigraphic thickness varies from 2.0 to 2.5 Km that comprises all the five formations (Soan, Nagri, Dhok Pathan, Kamlial and Chinji) of Siwalik group. The lithological composition of this zone is almost identical with their respective stratotype areas (Samiullah et al., 2011, 2015).

The Siwalik giraffid fauna was studied by Falconer and Cautley (1836), Falconer (1845), Forsyth-Major (1891), Pilgrim (1911), Bohlin (1926), Colbert (1933, 1935a), Lewis (1939), Churcher (1978), Akhtar et al. (1991), De Bonis et al. (1997), Franz-Odendaal and Solounias (2004), Samiullah (2011), Samiullah et al. (2011, 2012, 2015) and Tariq and Jahan (2014). The main aim of this study is to provide the knowledge of Giraffid fossils found in Dhok Bun Ameer Khatoon by highlighting the aspects of evolution, systematics and biogeographical distribution at specific level.

MATERIALS AND METHODS

The Miocene deposits of the Dhok Bun Ameer Khatoon were thoroughly investigated. Several field tours in 2014 and 2015 were carried out to the studied section and different fossils were collected. Surface collection was the primary method for fossil collection. Excavations were also conducted at some places, where dense concentrations of fossil bones occur in situ within sandstone. The embedded material was excavated by using chisels, penknives and geological hammers and fine needles and brushes. During excavation, disintegration of fossils was prevented by adopting careful measures. Each specimen was completely wrapped in cotton pieces which protect it from the shocks during transportation. Eventually the specimens collected from the site were brought to the Paleontology laboratory of Zoology Department, GC University Faisalabad for morphological and taxonomic analysis.

Dust particles were removed very carefully with the help of brushes which made the specimens clear for observation. Then the specimens were washed and cleaned with the help of citric acid. Clay and other adjoined sediments were removed by using GEMKA (engraving machine, BK industries, India) fine needles and brushes. Gums and resins like magic stone and elfy etc were used to rejoin the accidentally broken fragments of specimens. A magnifying lens (Triplet 10X18mm) was used for small and more ambiguous morphological characters. A digital vernier caliper was used for measurements that given in millimeters (mm). The catalogue number PC-GCUF 05/15 was allotted to the specimens that represent the serial number (numerator) and collection year (denominator). A digital camera was used to make photograph of the studied specimens and amended hard copies were prepared in the computer. Finally, the comparison was made with specimens from the Natural History Museum, London (BMNH), the American Museum of Natural History (AMNH), the Geological Survey of Pakistan (GSP), the Geological Survey of India (GSI), and the specimens from the Palaeontology laboratory of the Zoology Department of the Punjab University, Lahore, Pakistan (PUPC). The studied material was stored in the Palaeontology laboratory of the Department of Zoology, Government College University Faisalabad, Pakistan.

SYSTEMATIC PALEONTOLOGY

Order Artiodactyla Owen, 1848

Suborder Ruminantia Scopoli, 1777

Infraorder Pecora Linnaeus, 1758

Superfamily Giraffidea Gray, 1821

Family Giraffidae Gray, 1821

Subfamily Giraffinae Zittel, 1893

Genus Giraffokeryx Pilgrim, 1910

Type species: Giraffokeryx punjabiensis Pilgrim, 1910

Distribution

The genus Giraffokeryx is only known from the Lower to Middle Siwaliks (Pilgrim, 1910; Colbert, 1935).

Giraffokeryx punjabiensis Pilgrim, 1910

Type specimen

Lectotype GSI 502, a third molar M3 of right maxilla.

Locality

Chinji and vicinity, Salt Range Punjab.

Stratigraphic range

Lower Siwaliks, Chinji Formation and lower portion of the Middle Siwaliks.

Diagnosis

Giraffokeryx is a medium sized four horned giraffid, two at the frontal on anterior extremities and two on the fronto-parietal region. Posterior horn is hanging over the temporal fossae. Limbs and feet are certainly of medium length. Teeth are brachydont with prominent rugosity on enamel as in the other genera of Giraffidae (Pilgrim, 1910).

Distribution

The species are distributed in Lower Siwaliks as well as in Middle Siwaliks (Pilgrim, 1910; Colbert, 1935). The Lower Siwalik localities are Kamlial and Chinji Formation, district Attock and Chakwal respectively, within the province of Punjab, Pakistan. The locality of the Nagri zone is in the Nathot, Jhelum District of Punjab, Pakistan.

Specimens examined

PC-GCUF 01/14, left maxillar ramus having P3-M3; PC-GCUF 02/14, an isolated right third upper molar; PC-GCUF 03/14, an isolated right third upper molar; PC-GCUF 04/14, an isolated left fourth upper premolar; PC-GCUF 10/15, broken left second upper molar having protocone and metacone.

Descripition

PC-GCUF 01/14

It is a left maxilla with P3-M3 (Fig. 1). The length of maxilla is about 110 mm. P3 is damaged from anterior lingual side but P4, M1, M2, and M3 is excellently preserved. In P3 protocones and metacone are absent. It is a narrow-crowned tooth without definite boundary between the major cones. The central cavity is not completely observed due to the broken anterior side which also makes dentine visible from anterior lingual side. Moderately developed mesostyles and parastyles also observed. The P4 It is a low and broad crowned tooth having anterio-posterior length slightly less than the transverse width. Rugosity can be observed on the lingual side. Cingulum is absent and central cavity is shallow and wide. Moderately developed parastyle and mesostyle with well developed metastyle is observed. All the chief cusps are preserved with outer cusps slightly taller than the inner ones. The anterio-posterior length is little greater in the buccal side as compared to lingual side. Posterior side of the tooth is broken at the top. In M1 Median basal pillar and cingulum is absent. The outer cones are slightly larger in size as compared to the inner cones. The paracone is well developed and slightly broader in the middle having two sharp ridges running anterio-posteriorly. Anterior ridge touches the parastyle while posterior ridge is united with anterior side of metacone. Parastyle is preserved. Metacone is excellently developed, slightly higher in size than paracone. Crescentic hypocone has anterior and posterior limbs. Para-, meso- and metastyles are weakly developed. The anterior median rib is well developed as compared to posterior one. Narrow and less shallow anterior cavity compared to posterior central cavity is also present. In M2 the protocone at the anterior lingual side is well developed having anterior limb slightly taller than the posterior limb. The paracone in the anterio-buccal side is pointed towards the middle. It is connected to well develop metacone from posterior side. The mesostyle is well developed and anterior median rib is prominent but slightly broken from the top. The posterior median rib is almost disappeared. Parastyle is excellently developed. In M3 the wrinkles are more prominent on the lingual side compared to those of the buccal side. The median basal pillar is present but broken. The cingulum is absent. The major cones are very well developed and the outer cones are slightly taller than the inner cones. A well developed protocone is present on the anterio-lingual side of the tooth and is rounded in the middle. The anterior limb is larger than the posterior. The paracone is medially pointed and is present at the anterio-buccal side of the tooth. At the posterior side it is connected to the metacone which is well developed. The metacone is almost equal to the paracone. The mesostyle is well developed and broken. The slightly broken anterior median rib is more prominent than that of the posterior. The hypocone is present on the posterio-lingual side of the tooth and is well developed, having no connection with the protocone. The parastyle is prominent.

PC-GCUF 04/14

The specimen is an isolated left fourth upper premolar (Fig. 1). It is in the excellent stage of preservation. It is a low and broad crowned tooth having anterio-posterior length slightly less than the transverse width. Rugosity can be observed on the lingual side. Cingulum is absent and central cavity is shallow and wide. Moderately developed parastyle and mesostyle with well developed metastyle is observed. All the chief cusps are preserved with outer cusps slightly taller than the inner ones. The anterio-posterior length is little greater in the buccal side as compared to lingual side.

 

PC-GCUF 02/14

The tooth is an isolated right third upper molar in an excellent state of preservation (Fig. 1). It is brachyodont and narrow crowned. The enamel is very thick and rugose. The wrinkles are more prominent on the lingual side as compared to those of the buccal side. The median basal pillar is present but broken. The cingulum is absent. The major cones are very well developed and the outer cones are slightly taller than the inner cones. A well developed protocone is present on the anterio-lingual side of the tooth and is rounded in the middle. The anterior limb is larger than the posterior. The paracone is medially pointed and is present at the anterio-buccal side of the tooth. At the posterior side it is connected to the metacone which is well developed. The metacone is almost equal to the paracone. The mesostyle is well developed and broken. The slightly broken anterior median rib is more prominent than that of the posterior. The hypocone is present on the posterio-lingual side of the tooth and is well developed, having no connection with the protocone. The parastyle is prominent. The impression mark is absent on the posterior side of the tooth which confirms that the specimen under study is the last molar.

PC-GCUF 03/14

The tooth is in an excellent state of preservation. It is an isolated upper third molar (Fig. 1). It is brachyodont and narrow crowned. The enamel is very thick and rugose. The wrinkles are more prominent on the lingual side compared to those of the buccal side. The median basal pillar is present but broken. The cingulum is absent. The major cones are very well developed and the outer cones are slightly taller than the inner cones. A well developed protocone is present on the anterio-lingual side of the tooth and is rounded in the middle. The anterior limb is larger than the posterior. The paracone is medially pointed and is present at the anterio-buccal side of the tooth. At the posterior side it is connected to the metacone which is well developed. The metacone is almost equal to the paracone. The mesostyle is well developed and broken. The slightly broken anterior median rib is more prominent than that of the posterior. The hypocone is present on the posterio-lingual side of the tooth and is well developed, having no connection with the protocone. The parastyle is prominent. The impression mark is absent on the posterior side of the tooth which confirms that the specimen under study is the last molar.

PC-GCUF 10/15

It is broken left second molar having prominent protocone and metacone (Fig. 1). Rugosity is observable in the anterior lingual side. Parastyle and mesostyles are also in preserved state. Median rib is developed.

Comparison

The specimens described here are of typical giraffid type showing almost all the basic features, such as crescentic cusps, deep enamel and its rugose sculpture, comparatively weak styles and median ribs. In Giraffokeryx punjabiensis the external folds are reasonably more developed in the premolars, and in the under study specimens, the styles and median ribs are not much pronounced which is a characteristic of G. punjabiensis. Specimen PC-GCUF 01/14 is a left maxillary segment having P3-M3. When compared with AMNH 19475, PUPC 08/33, PUPC 08/43 and PUPC 08/98, it is evident that the anterio-posterior length and crown width can be compared favorably having narrow crown and the anterio-posterior length of the teeth is almost equal to the transverse width (Table I). Median ribs are missing while the styles are weakly preserved which indicate that specimens under study belong to G. punjabiensis.

 

Table I. Comparative measurements of the cheek teeth of Giraffokeryx punjabiensis in mm.

Number	Position	Length	Width	W/L
PC-GCUF 01/14	P3	18.5	19.5	96.2
AMNH 19475	P3	20.5	20	97.5
PUPC 08/33	P3	23	21.5	93.4
PUPC 08/43	P3	16	13	81.2
PUPC 08/98	P3	23	20	86.9
PC-GCUF 01/14	P4	17.5	24	137.1
PC-GCUF 04/14	P4	20	21.5	107.5
AMNH 19475	P4	7.5	21	120
AMNH 19330	P4	17	23	135.5
PUPC 08/26	P4	18.5	21	113.5
PUPC 08/96	P4	13.5	19	140.7
PC-GCUF 01/14	M1	25	24	96
AMNH 19334	M1	24	24	100
AMNH 19311	M1	25.5	25	98
PUPC O8/105	M1	24	23	95.8
PUPC 94/07	M1	25	17	68
PUPC 02/157	M1	20.5	21	102.4
PC-GCUF 01/14	M2	27.5	27	98.1
AMNH 19472	M2	27	25	92.5
AMNH 19611	M2	26	27	96.2
AMNH 19320	M2	29	28.5	98.2
PUPC 08/18	M2	28.5	27	94.7
PUPC 08/28	M2	30	29	96.6
PUPC 69/137	M2	29	29	100
PC-GCUF 01/14	M3	25.5	26	101.9
PC-GCUF 03/14	M3	30.5	33	108.1
PC-GCUF 02/14	M3	29.5	31	105S
AMNH 19325	M3	27.5	28	101.8
AMNH 19327	M3	23	23.5	102.1
AMNH 19475	M3	24.5	26	106
PUPC 08/117	M3	32.5	33	101.5
PUPC 66/95	M3	27	27	100

 

The specimens PC-GCUF 01/14 and PC-GCUF 04/14 are fourth upper left premolar that shows the striking resemblance with AMNH 19475, AMNH 19330, PUPC 08/26 and PUPC 08/96. All the teeth are broad crowned and show the typical morphology of this species. Moreover, crown width is slightly greater than the anterio-posterior length. Further more, the anterio-posterior length, transverse width and W/L ratio also closely related to the P4 of AMNH 19475 and others. In M1 of the specimen PC-GCUF 01/14, the median ribs along with styles are less pronounced and the measurements and tooth morphology resemble AMNH 19334, AMNH 19311, PUPC 08/105, PUPC 94/07 and PUPC 02/I57. The specimen PC-GCUF 01/14, together with the M1 in the AMNH collections and PUPC are narrow crowned. The M2 of PC-GCUF 01/14 is comparable to AMNH 19320, AMNH 19472, AMNH 19611, PUPC08/18, PUPC 08/28 and PUPC 69/137 (Table I). The M3 of PC-GCUF 01/14, PC-GCUF 02/14, the right upper third molar and PC-GCUF 03/14, right upper third molar is comparable to AMNH 19325, AMNH 19327, AMNH 19472, AMNH 19475, PUPC 08/117 and PUPC 66/95 having almost similar anterio-posterior lengths, crown widths and are narrow crowned. In the M3, the parastyle is more developed compared to the mesostyle and metastyle, while the posterior median rib is also missing (Colbert, 1935).

On the basis of tooth size, outline, enamel constriction and structure of crown, they resemblethe species G. punjabiensis. The P3 measurements described here clearly resemble to those given for AMNH 19475. They all have narrow crown and their W/L ratio also resemble with the type specimen. In Giraffokeryx, the styles are weak, median ribs are absent or poorly developed and the crown is narrow. The teeth under study also show the resemblance with typical morphology of G. punjabiensis. Slight differences in the measurements obtained are due to intraspecific variation. Consequently, all the specimens under study referred to G. punjabiensis. Table II and Figue 2 show comparison of the studied specimens with the type specimens and already described collection of upper dentition.

Genus Giraffa Brisson, 1762

Type species

Giraffa camelopardalis Linnaeus 1758

Included species

G. sivalensis Falconer and Cautley 1849; G. punjabiensis Pilgrim, 1910; G. priscilla Mathew, 1929.

Distribution

The genus Giraffa is known from Lower, Middle and Upper Siwaliks (Pilgrim, 1910; Mathew, 1929; Colbert, 1935). It is also found in Africa.

Giraffa priscilla Mathew, 1929

Type specimen

GSI B 511, a left M3.

Locality

Chinji, Salt range, Chakwal District, Punjab, Pakistan (Colbert, 1935).

Stratigraphic range

This species is only found in the Lower Siwaliks (Chinji Formation) of Pakistan.

Diagnosis

It distinguishes from Giraffokeryx by the broad and more brachyodont teeth, prominent styles (especially metastyle). Prominent anterior rib; in M3 the more oblique-set inner crescent, broad third lobe with strong accessory basal cusps in front of it, as well as shorter crown (Colbert, 1935).

Specimens examined

PC-GCUF 01/15, an isolated right firstupper molar; PC-GCUF 02/15, an isolated left second upper molar; PC-GCUF 08/15, right maxilla having M1-M3; PC-GCUF 09/15, an isolated right fourth upper premolar.

Description

PC-GCUF 09/15

It is an isolated right fourth premolar and in an excellent preserved state (Fig. 1). Antro-posterior length is almost equal to the transverse width of the specimen. It is low and broad crowned tooth having rugose and thick enamel. Cingulum is absent. The central fossette is prominent towards the anterior side. Major cusps and styles are preserved well and develop properly. Well developed median rib is observed in the specimen.

PC-GCUF 08/15

GCUF-PC 08/15 is a right maxilla with M1-M3 (Fig. 1). The length of maxilla is about 81 mm. The M1 is low crowned first upper molar of right maxilla. It is extremely brachydont broad crowned tooth having more prominent cingulum toward anterior side. The major cusps are fully developed in oblique angle to the axis of the tooth. The outer cusps are little higher vertically than the inner cusps. The crescentic protocone is present at the anterior lingual side. The metacone exists at the anterior buccal side of the tooth. The hypocone is well developed. The styles, meso-, para-, and metastyles are prominent. The anterior median rib is well developed but posterior one is moderately developed. In M2 the protocone is crescent shaped and united with paracone with the help of a thin layer of enamel to form parastyle. The paracone is in good preserved state located at the anterior side of the tooth. It is pointed towardsthe middle with two sloping ridges running antrio-posteriorly. The metacone is also preserved excellently pointed towards the middle with sloping ridges. Mesostyle is formed by the union of paracone and metacone. The hypocone is also well preserved. The parastyle is better preserved along with metastyle and mesostyle. The anterior median rib is prominent but broken at the top. The anterior central fossette is narrower than the posterior one. In M3 the Protocone is crescentric, joined with paracone to form parastyle. The paracone at the anterior side of the tooth is well preserved pointed towards the middle with two sloping antrio-posterior running ridges. The metacone is preserved efficiently pointed towards the middle with sloping ridges. The paracone and metacone assembled to form a mesostyle. The hypocone is preserved well but broken at the posterior side. The parastyle, metastyle and mesostyle are all in better preserved state. The median ribs are not prominent. The anterior central cavity is narrower than the posterior one.

PC-GCUF 01/15

The specimen under study is low crowned first upper molar of right maxilla (Fig. 1). It is in good state of preservation. The enamel is moderately thick and rugose. The rugosity is more prominent towards the lingual side as compared to buccal side. It is in the late stage of wear. Since the teeth are completely worn, the teeth must be belongs to some old individual. It is extremely brachydont and narrow crowned. The cingulum is more prominent toward anterior side. The length of the tooth is not in excess of the breadth. The major cusps are well developed. These are very oblique to the axis of the tooth. The outer cusps are slightly higher vertically than the inner cusps. The protocone is crescentic in shape and present at the anterior lingual side. The metacone located at the anterior buccal side. Due to late stage of wear, the metacone and paracone is connected to form a lope like structure. The hypocone is slightly damaged posteriorly. The styles are well developed. The median ribs are moderately developed.

PC-GCUF 02/15

It is an isolated upper low crowned second molar (Fig. 1). It is in late stage of wear. Its enamel is moderately thick and very rugose. Rugosity is more prominent towards the lingual side than buccal side. No cingulum and medial basal pillar in the transverse valley. Extremely brachyodont and broad crowned. The length of the tooth is not in excess of the breadth. The major cusps are well developed. The outer cusps are slightly higher vertically than the inner cusps. Protocon is crescentric and joined with paracone through a thin layer of enamel to form parastyle. The paracone is well preserved. It is located at the anterior side of the tooth. It is pointed in the middle with two sloping antroposterior running ridges. The metacone is slightly damaged posteriorly. It is pointed in the middle with sloping ridges. The paracone and metacone are connected to form a mesostyle. The hypocone is well preserved except posterior side which is missing. The parastyle is well preserved. The metastyle and mesostyle are slightly damaged. The median ribs are not prominent. The anterior central cavity is narrower than the posterior one. Small enamel is formed in the middle of the tooth due to late and advanced stage of wear.

Comparison and discussion

The described material comprises nine dental remains of giraffids from the Dhok Bun Amir Khatoon (Chinji Formation) of the Lower Siwaliks of Pakistan. Being squared and tetra tuberculated teeth; they all can be reffered to some herbivorous mammalian group. Since the cusps are crescentic in outline, it can safely be included in the sub order ruminantia of the order artiodactyla. Since the enamel is strongly rugose, the tooth can be referred to the family giraffidae. General characters of giraffid teeth are: low crowned brachydont teeth, enamel is moderately thick with prominent rugosity on the lingual side, absence of basal pillar in the transverse valley, outer cusps slightly higher as compare to inner ones, presence of all the major cones (protocone, paracone, metacone and hypocone) and of crescent shaped, anterior and posterior fossettes, median ribs may or may not prominent. All the specimens under study exhibit these characteristics. So, all belong to family Giraffidae.

Regarding size, giraffes can be placed into two forms (Sarwar and Akhtar, 1987). Small form includes the genera Giraffokeryx (Pilgrim, 1910) and Giraffa (Pilgrim, 1911) while the large one includes the genera Bramatherium (Falconer, 1845), Hydaspitherium sivatherium (Falconer and Cautley, 1845) and Vishnutherium (Colbert, 1935). Colbert (1935) gave the classification of Siwalik giraffes (Family Giraffidae) and divided it into three subfamilies i.e. Paleotraginae, Sivatheriinae and Giraffinae. Genus Giraffokeryx was placed in subfamily Paleotraginae, Sivatheriinae includes the Sivatherium, Bramatherium, Helladotherium and Hydaspitherium genera while Giraffa was placed in subfamily Giraffinae. The emergence of all these three subfamilies has occurred simultaneously but their migration took place at different times to the Siwalik region. Sivatheriines came later to this region than Palaeotragines and Giraffines (Akhtar, 1996). Hamilton (1978) modified and added two new subfamilies in the above mentioned classification of family Giraffidaeand divided it into five subfamilies i.e. Okapinae, Palaeotraginae, Sivatheriinae, Samotheriinae, Giraffinae and Palaeotraginae.

In genus Giraffa, styles and median ribs are strong and well pronounced and crown is slight broad while in Giraffokeryx weak styles, median ribs are absent and crown is slightly narrow. Giraffa punjabiensis is smaller species of genus Giraffa than G. sivalensis and G. camelopardalis. The upper premolars of this species are relatively smaller and narrow. G. sivalensis is larger than modern giraffe. The posterior half of third upper molar is reduced G. sivalensis. Camelopardalis affinis is similar to G. sivalensis in size but larger to the modern giraffe. In G. Priscilla, this broad and more brachyodont, prominent styles (especially metastyle), prominent anterior rib are observed. Parastyle is some what less developed as compared to the meso- and metastyle that are well developed. Posterior median rib is also present.

As characteristics mentioned above, it is evident that the specimens PC-GCUF 01/15, PC-GCUF 02/15, PC-GCUF 08/10 and PC-GCUF 09/15 belong to genus Giraffa and all the above mentioned feature sare comparable with type material GSI B 492 (described by Matthew, 1929), PUPC 02/99, PUPC 68/13 and GCUPC 1138/09 of the species G. priscilla. Therefore, it is concluded that, on the basis of above mentioned characters, the overall contour of the teeth, its size and enamel constriction and also the development of different crown structure, specimens are referred to species G. priscilla. Table II showing width/length indexes of cheek teeth of G. Priscilla and comparison of the studied specimens are also provided in Figure 2.

 

Table II. Comparative measurements of the cheek teeth of Giraffa priscilla in mm.

Number	Position	Length	Width	W/L
PC-GCUF 09/15	P4	23	22	95.6
PC-GCUF 01/15	M1	24	28	116
PC-GCUF 08/15	M1	29	28	96.5
PUPC 02/99	M1	24	24	100
PC-GCUF 08/15	M2	30	27	90
GCUF-PC 02/15	M2	28	29	103.5
PUPC 02/99	M2	25	28	112
PUPC 68/13	M2	25	27.5	110
GCUPC 1138/09	M2	25.2	28.6	113
PC-GCUF 08/15	M3	29	26	90

 

 

Evolution of giraffids

Heintz (1975) gave the concept about the evolution and phylogenetic relationship of family giraffidae which was further modified by Mitchell and Skinner (2003). According to Heintz (1975), the evolution of giraffe started from dear. It was just after the Eumeryx. The Climacoceras were first giraffid to be appeared in very earliest Miocene. Then Canthumeryx appeared in very early Miocene, Paleomeryx and finally the short necked giraffids the “Palaeotragus” in early Miocene. This lineage through Samotherium (giraffes of late Miocene) split into a short necked Okapia having one species still alive and the modern long necked giraffes known as Giraffa. He arranged the evolution in following order: (1) Canthumeryx, (2) Palaeomeryx, (3) Palaeotragus, (4) Samotherium, (5) Giraffa.

Mitchell and Skinner (2003) modified the evolutionary concept of giraffe given by Heintz. They described that the okapi and giraffe (both have one extant species) have evolved from the Canthumerycids through the intermediate extinct forms of Giraffokeryx, Palaeotragus, Samotherium and Bohlinia. The order according to Mitchell and Skinner (2003) is thus:(1) Canthumeryx were the most primitive giraffes appeared about 22.8–11.2 million years before present (2a) Giraffokeryx lived 17.2–5.3 million years before present simultaneously with Canthumeryx (2b) Palaeomeryx lived about 15 Million years ago (3) Palaeotragus were appeared about 18–1.76 million years before present (4) Samotherium about 14.6–3.4 million years before present (5) Bohlinia about 11.2–5.3 million years before present (6) Giraffa about 12 million years to present (7) Okapia is a descendent from Samotherium, but according to Mitchell and Skinner Okapiais “the extant form” of Palaeotragus appeared about 18 million years to present.

Palaeoenvironment and feeding habits

Physical and ecological characteristics of habitat are directly related to the dietary habits of the animals (Kingston and Harrison, 2007). In Asia, warm tropical and subtropical forest zones are represented in the Miocene period of Siwalik sequence (Northern Pakistan). The floral as well as faunal components of that period are quite comparable to the early Late Miocene of Europe (Barry et al., 1985). The rainy humid environment was due to the persistency of the forested environment in Africa. The fauna of Dhok Bun Ameer Khatoon mainly contains of Artiodactyla (tragulids, bovids giraffids, suids and cervids) and Perissodactyla (rhinocerose). In the present collection Giraffids were collected from the fossiliferous site. The association of Crocodilian skutes and isolated teeth of Gaindatherium browni, Deinotherium, Listriodon pentapotamiae, Dorcatherium minus, Dorcatherium majus, Giraffokeryx punjabiensis, Giraffa priscilla, Cervus punjabiensis, and Gazella lydekkeri in the site, justifying that they probably had almost the same feeding resources at that time period (Samiullah, 2011).

The giraffid remains in this study justify the vegetation of Chinji Formation as seasonal woodland with riparian areas of forest. The presence of giraffids in Chinji to Nagri Formation indicates that the composition of the Siwaliks was change from seasonal woodland to tree savannas. Giraffokeryx punjabiensis was a mixed feeder and was better adapted to a life in savannas. They can with stand without drinking water for weeks and rely on dew drops in the morning and water contents of their food (Janis and Scott, 1987; Franz-odendaal and Solounias, 2004). It was thought that the diet of fossil Giraffids was to be similar to that of extant giraffes (committed browsers). Solounias (1988) studied the extinct giraffid Samotherium boissieri from the Miocene rocks of Greece (Samos) and declared it as a mixed feeder-grazer. This study had changed the notion that all Giraffids are browser. The heterogeneous diet of Giraffid fossils was further confirmed by tooth microwear analyses and premaxillary shape (Solounias and Moelleken, 1993). Among sivatheriinae the Bramatherium megacephalum and Sivatherium giganteum (Falconer and Cautley, 1836) were probably grazers but Helladotherium duvemoyi was a browser. The Giraffokeryx punjabensis (Pilgrim, 1910) was a mixed feeder where as Palaeotragus primaevus (Churcher, 1978) was a browser. Among the Giraffinae (Pilgrim, 1911) there are also browsing, grazing and mixed feeding taxas. In addition, Solounias and Semprebon (2002) found that the Okapia johnstoni (Sclater, 1900), the second and rare extant species of Giraffidae, is not a browser but a fruit-dominated browser while the other extant species the Giraffa camelopardalis (Linnaeus, 1758) can be redefined as a leaf-dominated browser. Such dietary data suggest that the grazing in family Giraffidae was started before the expansion of C4 grasslands. Some giraffids were mixed feeders around 6 to 8 Ma (Cerling et al., 1997; Harris and Cerling 1998), and they were feeding as such on C3 grasses, which were dominated in woodland environments in open meadows and near the margins of water.

Biostratigrphy

The Giraffokerycinae appeared sporadically in the Chinji beds of the Siwaliks (Bhatti et al., 2007). Giraffokeryx punjabiensis has been documented from several localities of Siwalik late Middle Miocene (Bhatti, 2005), occupying a long geochronologic ranges from Western Europe to Indian subcontinent (Bohlin, 1926; Bosscha-Erdbrink, 1977; Gentry et al., 1999). G. punjabiensis, in association with Listriodon pentapotamiae, Conohyuss indiensis, Gaindatherium browni, Brachypotherium fatehjangense, Sivapithecus sp and Deinotherium pentapotamie are considered to be zonal marker elements of Chinji Formation (Barry et al., 2002). The Chinji fauna is in favour of Middle Miocene age because the comparison of the material with several representatives of the fauna indicates a Middle Miocene age (Pilgrim, 1937, 1939). The faunal assemblage contains elements significant enough to be compared with Astaracian of Europe and Greco-Iranian Province spanning from middle Miocene to earliest Late Miocene (Khan et al., 2011). It shows overlapping of temporal ranges with that of the Chinji stratotype which correspond to the MN6 as well as MN7/8 (Colbert, 1935).

CONCLUSION

During the Late Miocene, the Lower Siwaliks were mainly characterized by the presence of two species of small-sized giraffids: Giraffokeryx punjabiensis and Giraffa priscilla. The presence of Giraffokeryx in the Late Miocene of the Siwaliks and the Greco-Irano-Afganian province implies at this time, the Himalayan Mountains did not act as a barrier in the dispersal of the fauna out of southern Asia. The range contraction of this species suggests that it occupied a wide territory from the Subcontinent to the Greco Irano-Afganian in Late Miocene of the Siwaliks. The paleoecology of studied taxon reveals the persistence of mosaics of diverse habitats ranging from tropical evergreen forests to subtropical ones, closed and seasonal woodlands to wooded savannas. The age of the fossils collected and studied from the Dhok Bun Ameer Khatoon is clearly later than the early Miocene, and also, they appear to be earlier than the Pliocene.

Statement of conflict of interest

The authors have declared no conflict of interest.

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