Proceso de comparación entre metodologías

Post-crania

Standard measures are the same as those described for canids (section 3.38; fig.3.31). As discussed in section 3.2.1, a multi-species study could not be carried out for the Family Hyaenidae and so mass estimates for British Pleistocene C. crocuta were made by simple comparison with modem skeletons, assuming geometric scaling.

Metapodials were excluded firom the analysis as these elements are proportionally reduced in comparison to modem spotted hyaenas (Tumer 1981).

Teeth

Tooth measurements for hyaenids were exactly as described for canids (section 3.3.8; fig.3.34). Mass estimates were produced by geometric comparison o f mi measure © with the average length o f mi fi*om modem populations.

3.3.11 Felidae

Post-crania

Standard measures are the same as those described for canids (section 3.38; fig.3.31). The mass estimating equations developed for this Family are given in Appendix 3.1.6c. For elements with sufficient sample sizes to allow comparison e.g. astragalus, consistent estimation between measures was demonstrated (fig.3.38). Due to the findings o f other scaling studies, mass estimates fi"om length measures o f the radius, tibia and metapodials were excluded fi*om mass averages. Consistent estimation o f mass among the majority o f bones was achieved. This is demonstrated using the largest British Pleistocene felid assemblage available, P. leo fi*om the Stage 7 site o f Bleadon Cave, Somerset (fig.3.39). The only problem area is the high mass estimate produced fi*om the scapula, so these mass estimates were discarded.

45 0 40 0 O) 350 - 300 -

-S'

Asti Ast2 Ast3 Ast4 Ast7

Measure

Fig.3.38: Body m asses estimated for P. leo from the Stage 7 site o f Bleadon Cave, Somerset using various standard measures o f the astragalus. Points represent the average estimated mass; error bars the sample standard deviation. Sample size for all measures n = 7.

4 5 0 4 0 0 350 300 250 200 g 150

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Fig.3.39: Comparison o f body m asses estimated for Bleadon Cave Panthera leo from different post- cranial bone elements. Points represent the average estimated mass; error bars the sample standard deviation. The sample size o f mass estimates from each bone type is indicated.

Teeth

Tooth measures for felids are exactly as described for canids (section 3.3.8; fig.3.34). Once again, mass estimates were only produced fi-om the mi (Van

Valkenburgh 1990; Appendix 3.2.5). Length o f mi may be the most accurate estimator o f body mass in felids (Van Valkenburgh 1990). The close relationship between tooth size and body size is proposed to derive fi'om the extreme dental specializations o f felids. The mi equation worked well in estimating the body masses o f British

Pleistocene cats, producing mass values very close to the post-cranial estimate using the Bleadon cave sample (fig.3.37).

3.3.12 Summary

As many estimates o f mass as possible should be pooled to produce an average body mass result for a species from its skeletal remains. Comparison o f mass estimates produced jfrom measurements within the same bone element reveal aberrant results that need to be excluded fi-om the combined body mass averages. There are generally length measures o f distal limb elements but measurements that are difficult to take repeatably, or locomotor specialisations unique to individual species can also introduce problems. Once such data had been removed consistent mass estimates were produced for all o f the Families across bone types. This indicates that the mass estimating equations are operating successfully.

The regression statistics for the dental mass estimating equations generally indicate a weaker relationship between dimensions and mass than for post-crania. Different elements generally do not produce consistent mass estimates, especially when combined taxon or functional groupings are used to build up scaling equations. In most cases the mass estimates fi*om molars have been used, with the results fi-om pre-molars discarded. The mass results fi-om post-cranial and dental material are to be analysed separately due to several factors implying the lower reliability o f estimates produced using teeth.

No indication o f the accuracy o f the mass estimates produced firom Pleistocene fossil material can be given as the true body masses o f these forms is not known. Analysis o f modem material o f known mass using these methods has suggested that estimates within 15% o f actual can be produced in the majority o f cases using the post­ crania o f bovids, cervids, equids and suids (Scott 1990). The body masses o f modem animals are very difiScult to measure accurately due to seasonal fluctuations in fat levels and gut contents. Published mass data ofien only provide a generalised species

average, and it likely that an equivalent accuracy can be achieved from Pleistocene fossil material Such data can be used to provide a large amount o f palaeobiological information on mass trends through time (Chapters 4-6), the relationship between body size and environment (Chapter 7) and body size distributions within Pleistocene

communities (Chapter 8).