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Patterns of craniofacial variation and taxonomic diversity in the South African Cercopithecidae fossil record

Tesla A. Monson, Marianne F. Brasil, Dominic J. Stratford, and Leslea J. Hlusko

Plain Language Abstract

South Africa has played a central role in our understanding of human evolution. However, the difficulty associated with dating fossils recovered from South African caves has placed a large burden on the accurate interpretation of species associated with hominids, which are used as indicators of the age of deposits, or 'biochronological markers'. Old World Monkeys (OWMs) are frequent biochronological markers at these sites, with dated fossils from eastern Africa being used to date South African sites where the same species are present. The interpretation of fossil OWM taxa relies heavily on morphology, particularly cranial and dental remains. Many of the analytical methods used to interpret the taxonomy of this group also rely on the assumption that the cranial and dental traits are developmentally, functionally, and genetically independent, an assumption that has been increasingly questioned. We statistically explored cranial variation in South African fossil OWMs (n = 99) to determine whether or not extinct taxa reflect the same morphological patterns of variation as has been reported for extant groups. Our results show that many of the cranial measurements are statistically significantly correlated and fail to distinguish between species or even genera of fossil OWMs despite the fact that these measurements do distinguish between extant species. Overall, our results suggest that these extinct OWM taxa cannot be discriminated using cranial measurements alone, or that the taxonomic designations, as they currently stand, are confounded.

Glossary:
OWM – Old World Monkey
Modules – interrelated suites of traits
Papionins – members of Tribe Papionini, Family Cercopithecidae
Cercopithecids – members of Family Cercopithecidae

Resumen en Español

Patrones de variación craneofacial y diversidad taxonómica en el registro fósil de Cercopithecidae de Sudáfrica

El rico registro paleontológico de Sudáfrica es capital en nuestra comprensión de la evolución de los mamíferos del Plio-Pleistoceno debido en gran parte al número de cráneos recuperados. Debido a la dificultad del control cronométrico, en muchos de los sistemas de cuevas de los cuales proceden estos fósiles, a menudo se emplean los Monos del Viejo Mundo extintos (OWMs) como marcadores biocronológicos, por lo que la identificación taxonómica de estos restos de primates es particularmente relevante para hacerse preguntas evolutivas más amplias relacionadas con la evolución humana y los cambios de diversidad faunística. Las relaciones taxonómicas de los fósiles OWM se reconstruyen a través de la sistemática filogenética que depende en gran medida de los caracteres craneodentales. Estos métodos analíticos suponen que estos caracteres son independientes respecto al desarrollo, la funcionalidad y la genética. Esta suposición es cada vez más cuestionada por los análisis de datos fenotípicos existentes y por la genética. Se estudió estadísticamente la variación craneal en los Papionini fósiles sudafricanos (n = 99) para determinar si los taxones extintos reflejan la misma estructura de covarianza fenotípica que se ha establecido para los OWM existentes. Nuestros resultados muestran que muchas de las mediciones craneales están correlacionadas estadísticamente y no distinguen entre especies o incluso géneros de Papionini fósiles a pesar de distinguir especies existentes. En general, nuestros resultados sugieren que estos taxones extintos OWM no pueden ser discriminados utilizando mediciones craneofaciales únicamente, o que las designaciones taxonómicas, tal como están establecidas actualmente, son confusas.

Palabras clave: Monos del Viejo Mundo; Pleistoceno; Taxonomía; Papionini; morfología; covariación fenotípica

Traducción: Enrique Peñalver (Sociedad Española de Paleontología)

Résumé en Français

Schémas de variation crânio-faciale et diversité taxinomique dans le registre fossile sud-africain des Cercopithecidae
Le riche registre paléontologique d'Afrique du Sud est central pour la compréhension de l'évolution des mammifères au Plio-Pléistocène en grande partie grâce au grand nombre de crânes trouvés. Afin de pallier les difficultés de contrôle chronologique des nombreux systèmes de grottes d'où proviennent ces fossiles, les Singes de l'Ancien Monde (« Old World Monkeys », OWM) sont fréquemment utilisés comme marqueurs biochronologiques, ce qui rend l'identification taxinomique de ces restes de primates particulièrement pertinente pour explorer des questions évolutives plus larges liées à l'évolution humaine et aux changements de diversité des faunes. Les relations taxinomiques des fossiles d'OWM sont reconstruites par la systématique phylogénétique qui s'appuie fortement sur les traits crânio-dentaires. Ces méthodes analytiques supposent que ces caractères sont indépendants en termes de développement, fonction, et génétique. Cette hypothèse est de plus en plus remise en cause par des analyses de jeux de données sur le phénotype et le génotype des espèces actuelles. Nous avons exploré statistiquement la variation crânienne des Papionini sud-africains fossiles (n = 99) pour déterminer si les taxons éteints présentaient la même structure de covariance phénotypique que celle des OWM actuels. Nos résultats montrent que de nombreuses mesures crâniennes sont significativement corrélées et ne permettent pas de distinguer les espèces et même les genres de Papionini fossiles alors que ces mêmes mesures distinguent les espèces actuelles. En général, nos résultats suggèrent que ces taxons éteints d'OWM ne peuvent pas être discriminés en n'utilisant que des mesures crânio-faciales, et que leurs appellations taxinomiques actuelles prêtent à confusion.

Mots-clés : Singes de l'Ancien Monde ; Pléistocène ; taxinomie ; Papionini ; morphologie ; covariation phénotypique

Translator: Antoine Souron

Deutsche Zusammenfassung

Kraniofaziale Variations-Modelle und taxonomische Diversität im südafrikanischen Fossilbericht der Cercopithecidae

Der reichhaltige paläontologische Nachweis von Südafrika ist ein wesentlicher Bestandteil unseres Verständnisses der plio-pleistozänenen Säugetierevolution, der zum großen Teil der Anzahl der Schädelfunde zu verdanken ist. Wegen der schwierigen chronometrischen Kontrolle vieler Höhlensysteme aus denen die Fossilien stammen, werden oft ausgestorbene Altweltaffen als biochronologische Marker benutzt, was die taxonomische Zuordnung dieser Primatenüberreste besonders wichtig bei der Frage nach der Evolution des Menschen und Diversitätsveränderungen macht.
Die taxonomischen Beziehungen der Altweltaffen wurden mit phylogenetischer Systematik rekonstruiert, die stark auf craniodentalen Merkmalen beruht. Diese analytischen Methoden setzen voraus, dass diese Merkmale entwicklungstechnisch, funktional und genetisch unabhängig sind. Diese Annahme wird jedoch zunehmend durch Analysen von heutigen phänotypischen Datensätzen und der Genetik in Frage gestellt. Wir untersuchten statistisch kraniale Variation bei fossilen südafrikanischen Papioninen (n = 99) um zu bestimmen, ob ausgestorbene Taxa dieselbe phänotypische Kovarianz-Struktur reflektieren wie es für Altweltaffen beschrieben wurde. Unsere Ergebnisse zeigen, dass viele kranialen Maße statistisch signifikant korreliert sind und daher keine Unterscheidungen zwischen Arten oder sogar Gattungen fossiler Papioninen getroffen werden können, trotz der Unterscheidung heutiger Arten. Allgemein legen unsere Ergebnisse nahe, dass diese ausgestorbenen Altweltaffen nicht alleine auf kraniofaziale Messwerte reduziert werden können oder, dass sie nach gegenwärtigem Stand, unstrukturiert sind.

Schlüsselwörter: Altweltaffen; Pleistozän; Taxonomie; Papionini; Morphologie; phänotypische Kovariation

Translator: Eva Gebauer

Arabic

Translator: Ashraf M.T. Elewa

 

 

FIGURE 1. Six of the fossil cercopithecid specimens used in this study. 1, UCMP 125854, Papio izodi. 2, UCMP 125856, Papio izodi. 3, MP221, Parapapio jonesi. 4, TP9, Procercocebus antiquus. 5, MP222, Theropithecus darti. 6, STS394A, Cercopithecoides williamsi.

figure1

FIGURE 2. Bivariate plots of cranial measurements of extant papionins and the fossil sample. 1 and 2, Bivariate plot comparing cranial length and cranial breadth in extant papionins (1) and the fossil sample (2). 3 and 4, Bivariate plot comparing face length and muzzle width (ectomolare) in extant papionins (3) and the fossil sample (4). Note high correlations and the lack of a consistent taxonomic pattern across the distribution of fossil specimens. All bivariate correlations are significant at p < 0.0004.

figure2

FIGURE 3. Principle components analyses (PCA) of cranial variation in extant papionins and the fossil sample. 1 and 2, PCA including maximum cranial length, orbital width, interorbital breadth, and palate length raw measurements for 81 extant papionins (1) and 25 fossil cercopithecids (2). PC1 and PC2 of the extant sample comprise 82.2% and 8.1% of the variation, respectively, and PC1 and PC2 of the fossil sample comprise 67.8% and 21.6% of the variation, respectively. Note how well the measurements discriminate extant species, and how Papio h. ursinus (TM211) and one specimen of Theropithecus darti (TP9) are distinct from the other fossils. 3 and 4, PCA including orbital width, interorbital breadth, muzzle width (ectomolare), maximum width (canine), palate width (M3), palate width (canine), and palate length in 81 extant papionins (3) and 33 fossil cercopithecids (4). PC1 and PC2 of the extant sample comprise 86.6% and 4.8% of the variation, respectively, and PC1 and PC2 of the fossil sample comprise 66.1% and 12.7% of the variation, respectively. Note how well the measurements discriminate extant species, and that Cercopithecoides and Papio hamadryas are distinct from the other fossils.

figure3

 

TABLE 1. Genera and species represented, repository information, sample sizes, and specimen numbers used in this study. U Wits: University of the Witwatersrand, Johannesburg, South Africa; UCMP: University of California Museum of Paleontology, Berkeley, California, USA; Ditsong: Ditsong National Museum of Natural History, Pretoria, South Africa. TM211 was originally described as Papio spelaeus (Broom, 1936). M3147 has also been published as P. h. robinsoni (Gilbert et al., 2015).

Genus Species Repository N Specimen numbers Site(s) References
Cercopithecoides C. molletti Ditsong 1 SK551 Swartkrans McKee et al. (2011)
  C. williamsi Ditsong 3 KA195, KB5241C, MP36 Kromdraii, Makapansgat Szalay and Delson (1979), McKee et al. (2011), Geissler (2013)
    U Wits 1 STS394A Sterkfontein Geissler (2013)
    Total 5      
Dinopithecus D. ingens Ditsong 5 SK553, SK554, SK599, SK600, SK604 Swartkrans Gilbert (2013)
    Total 5      
Gorgopithecus G. major Ditsong 3 KA153, KA605, KA944 Kromdraii Gilbert (2013)
    Total 3      
Papio P. angusticeps Ditsong 5 CO100, CO101, CO102, CO135A, KA194 Cooper's Cave, Kromdraii McKee and Keyser (1994), Williams et al. (2007), Gilbert (2013)
  P. h. robinsoni Ditsong 5 SK555, SK557, SK558, SK560, SK562 Swartkrans Carter (2006), Geissler (2013), Beaudet et al. (2016)
    UCMP 2 UCMP 56767, UCMP 56797 Bolt's Farm Freedman (1965)
    U Wits 1 SWP31 Sterkfontein Eisenhart (1974)
  P. h. ursinus Ditsong 1 TM211   Freedman (1957)
  P. izodi U Wits 5 T89-11-1, TP4, TP7, TP10, TP12 Taung Gilbert and Grine (2010), Gilbert (2013)
    Total 19      
Parapapio P. broomi Ditsong 6 STS254A, STS262, STS393, STS396A, STS397, STS564 Sterkfontein Carter (2006), Williams et al. (2007), Gilbert (2013)
    UCMP 1 UCMP 56786 Bolt's Farm Freedman (1965)
    U Wits 7 M3056, M3065, MP151, MP2, MP224, MP76, SWP12 Makapansgat, Sterkfontein Fourie (2006), Fourie et al. (2008), Gilbert (2013)
  P. jonesi Ditsong 2 STS260, STS565 Sterkfontein Pickering et al. (2004), Fourie et al. (2008), Gilbert (2013)
    U Wits 5 M3060, MP75, MP173, SWP389, SWP2947 Makapansgat, Sterkfontein Maier (1970)
  P. whitei UCMP 1 UCMP 56614 Buxton Limeworks Freedman (1965)
    U Wits 10 BF43, M3070, M3072, M3147, MP119, MP164, MP208, MP221, MP223, MP239 Bolt's Farm, Makapansgat Maier (1977), Williams et al. (2007), Fourie et al. (2008), Williams (2013)
  unknown U Wits 4 M3053, M3084, M3133, MP47 Makapansgat Fourie (2006), Fourie et al. (2008)
    Total 36      
Procercocebus P. antiquus UCMP 3 UCMP 56609, UCMP 56694, UCMP 125956 Buxton Limeworks Gilbert (2007)
    U Wits 5 M3078, M3079, T89-154, TP8, TP9 Makapansgat, Taung Gilbert (2013)
    Total 8      
Theropithecus T. darti U Wits 4 M3073, MP168, MP217, MP222 Makapansgat Maier (1972), Williams et al. (2007), Geissler (2013), Gilbert (2013)
  T. oswaldi Ditsong 2 SK561, SK563 Swartkrans Folinsbee and Reisz (2013)
    Total 6      
unknown unknown Ditsong 6 SB2, SK3, SK556, SK814, SKII25, STS537 Swartkrans, Sterkfontein N/A
    UCMP 1 UCMP 218738 Buxton Limeworks Monson et al. (2015)
    U Wits 10 unnumbered black skull, MP4A, SP1, SP24, SWP1728, SWP1731, SWP29, SWP2953, T8817, T9087 Makapansgat, Sterkfontein, Taung N/A
    Total 17      
TOTAL     99      

 

 

 

TABLE 2. Extant papionin species represented and sample sizes used in this study. All specimens are from the National Museum of Natural History in Washington D.C., USA, with the exception of one Theropithecus specimen from the National Museum in Addis Ababa, Ethiopia.

Species Sample size (n)
Cercocebus torquatus 20
Lophocebus albigena 15
Mandrillus sphinx 7
Papio hamadryas 34
Theropithecus gelada 5
Total 81

 

 

 

TABLE 3. Definitions of cranial measurements.

Measurement Definition
Maximum length Maximum length of the cranium from prosthion to inion.
Maximum breadth Maximum breadth of the cranium posterior to the external auditory meatus.
Orbital width Maximum width of the orbit along a line perpendicular to the orbital height.
Orbital height Maximum height of the orbit along a parasagittal plane.
Interorbital breadth Breadth between the superomedial margins of the orbits.
Nasal width Maximum width of the nasal aperture, from left to right alare.
Nasal height Maximum height of the nasal aperture, from nasospinale to rhinion.
Muzzle width (ectomolare) Maximum width of the muzzle, measured at the ectomolare.
Muzzle width (maxillary fossae) Maximum width of the muzzle, measured at the superior border of the maxillary fossae, inferior to the orbits.
Maximum width (canine) Maximum width of the muzzle, measured at the canine alveoli.
Maximum zygofrontal width Maximum width of the upper face, measured from left to right frontomalare temporale.
Maximum calvarial width (post-orbital constriction) Maximum calvarial width, measured at the post-orbital constriction.
Calvarial length Maximum calvarial length, measured from ophryon to inion.
Palate width (M3) Maximum width of the palate, measured from the lateral edges of the depth of the palate, along a line bisecting the third molars.
Palate width (canine) Maximum width of the palate, measured from the lateral edges of the depth of the palate, along a line bisecting the most medial points of the canine alveoli.
Palate length Maximum length of the palate, measured from orale to staphylion.
Face length Projection of the face, measured from prosthion to glabella.

 

 

 

TABLE 4. Sample size, mean, and standard deviation of each measurement for the fossil genera sampled in this study. All measurements are in millimeters.

Genus

Cercopithecoides

Dinopithecus

Gorgopithecus

Papio

Parapapio

Procercocebus

Theropithecus

Unknown

Sample size 5 5 3 19 36 8 6 17
Statistic Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
Maximum length 124.9 NA 173.9 21.7 NA NA 148.2 9.8 152.4 19.9 147.9 16.5 171.5 8.1 163.9 30.6
Maximum  breadth 81.6 6.2 87.1 5.9 NA NA 71.6 2.0 76.2 5.5 70.9 7.2 84.1 5.3 77.6 6.6
Orbital  width 29.4 2.2 30.1 6.0 NA NA 27.5 1.9 26.9 2.2 26.4 1.6 28.7 2.4 27.0 2.3
Orbital  height 27.9 0.8 30.1 6.0 NA NA 24.3 3.0 24.5 2.4 23.5 1.5 26.9 4.9 25.3 3.5
Interorbital  15.0 2.9 11.9 5.9 NA NA 11.5 2.7 11.4 2.0 8.9 1.2 12.1 1.5 11.8 2.4
Nasal width 14.9 2.5 16.1 3.5 16.4 NA 19.1 4.0 17.6 2.4 17.7 1.8 18.9 1.7 18.0 2.0
Nasal height 18.8 NA 27.6 1.8 NA NA 29.8 9.1 26.5 4.2 25.8 2.7 29.3 2.4 29.3 8.0
Muzzle width 
(ectomolare)
44.6 2.2 58.6 10.2 58.2 NA 51.4 8.0 51.2 4.2 46.8 2.4 51.9 3.1 48.1 6.6
Muzzle width  
(maxillary fossae)
25.5 3.9 39.9 5.8 NA NA 40.0 8.9 37.1 4.4 36.4 4.2 35.5 4.5 39.4 5.4
Maximum width (C) 30.6 2.7 38.7 9.4 43.0 3.4 41.4 11.3 36.6 5.8 35.2 4.1 33.8 2.1 38.6 4.8
Maximum zygofrontal width 81.0 3.2 88.1 21.3 NA NA 72.4 6.5 72.4 6.9 75.8 4.9 77.1 1.1 80.5 5.4
Maximum cal. width 54.9 3.8 54.1 0.9 NA NA 53.4 5.8 53.3 3.0 56.4 3.6 48.2 4.7 53.4 3.5
Calvarial length 94.4 10.7 92.3 NA NA NA 88.5 3.5 94.3 8.3 87.9 4.7 95.4 10.5 90.8 6.6
Palate width (M3) 19.2 1.5 25.1 6.9 25.9 7.1 23.9 5.2 24.1 2.3 20.5 2.7 24.3 4.7 21.2 2.9
Palate width (C) 18.8 1.8 27.8 8.1 23.6 0.0 24.2 6.2 21.5 3.0 17.8 2.8 20.4 1.1 22.0 3.0
Palate length 40.4 2.1 68.9 10.5 65.5 4.4 67.4 16.9 51.5 8.2 51.2 6.0 62.9 3.8 57.6 11.7
Face length 62.4 6.5 98.7 29.7 NA NA 99.0 30.7 82.2 11.6 76.1 10.6 93.0 0.9 94.0 28.6

 

 

TABLE 5. Results of the MANOVA for the extant and fossil papionins. Double asterisks denote significance at p < 0.001.

Traits Group p
Max. length, Max. breadth, Orb. width, Orb. height, Interorb. breadth, Nas. width, Nas. height, Muz. width (ecto.), Muz. width (max. fos.), Max. cal. width Extant 0.000**
Max. length, Max. breadth, Orb. width, Orb. height, Interorb. breadth, Nas. width, Nas. height, Muz. width (ecto.), Muz. width (max. fos.), Max. cal. width Fossil 0.439
Cal. length, Palate width (M3), Palate width (C), Palate length, Face length Extant 0.000**
Cal. length, Palate width (M3), Palate width (C), Palate length, Face length Fossil 0.382

 

 

 

TABLE 6. ANOVA results for the size-corrected values of the extant sample, n = 81. MANOVA is significant at p < 2.2e-16. Measurements are size-corrected using geometric mean (Mosimann, 1970). Shaded cells are significant at p < 0.05.

Genus comparison Muz. Width
(Ecto.)
Muz. Width
(Canine)
Palate Width (Canine) Palate Length Face Length
Lophocebus-Cercocebus 0.087 0.017 0.017 0.980 0.036
Mandrillus-Cercocebus 0.000 0.712 0.712 0.000 0.002
Papio-Cercocebus 0.000 0.040 0.040 0.000 0.000
Theropithecus-Cercocebus 1.000 0.224 0.224 0.000 0.000
Mandrillus-Lophocebus 0.000 0.007 0.007 0.000 0.000
Papio-Lophocebus 0.000 0.000 0.000 0.000 0.000
Theropithecus-Lophocebus 0.522 0.001 0.001 0.000 0.000
Papio-Mandrillus 0.192 0.987 0.987 0.991 0.024
Theropithecus-Mandrillus 0.000 0.938 0.938 0.007 0.438
Theropithecus-Papio 0.000 0.986 0.986 0.000 0.957

 

 

 

 

TABLE 7. ANOVA results for a subset of the size-corrected values of the fossil sample, n = 38. MANOVA is significant at p < 0.0009. Measurements are size-corrected using geometric mean (Mosimann, 1970). Shaded cells are significant at p < 0.05.

Genus Comparison Muz. Width
(Ecto.)
Muz. Width
(Canine)
Palate Width (Canine) Palate Length Face Length
Dinopithecus-Cercopithecoides 0.404 0.687 0.991 0.140 0.355
Papio-Cercopithecoides 0.035 0.966 0.930 0.004 0.300
Parapapio-Cercopithecoides 0.876 0.998 1.000 0.980 0.853
Procercocebus-Cercopithecoides 0.855 0.999 0.504 0.301 0.771
Theropithecus-Cercopithecoides 0.733 0.152 0.647 0.011 0.088
Papio-Dinopithecus 0.975 0.895 1.000 0.966 0.998
Parapapio-Dinopithecus 0.682 0.651 0.981 0.103 0.642
Procercocebus-Dinopithecus 0.855 0.318 0.892 0.938 0.882
Theropithecus-Dinopithecus 0.958 0.963 0.954 0.982 0.998
Parapapio-Papio 0.005 0.979 0.607 0.000 0.421
Procercocebus-Papio 0.099 0.605 0.800 0.167 0.912
Theropithecus-Papio 0.292 0.150 0.932 1.000 0.842
Procercocebus-Parapapio 1.000 0.837 0.090 0.169 0.997
Theropithecus-Parapapio 0.983 0.025 0.236 0.001 0.089
Theropithecus-Procercocebus 0.999 0.011 1.000 0.342 0.400

 

 

 

 

TABLE 8. Sample size and correlations for a subset of size-corrected measurement comparisons. A full correlation matrix comparing all size-corrected measurements is available in Appendix 8. All correlations are significant at p < 0.0004. “(C)” is the abbreviation for canine.

Measurement pair Sample size
(n)
Correlation
(r)
Maximum length - face length 31 0.898
Maximum  length - palate length 35 0.880
Maximum  zygofrontal width - orbital width 32 0.835
Palate length - face length 45 0.827
Maximum  length - maximum breadth 29 0.817
Maximum  length - calvarial length 31 0.814
Maximum  width (C) - palate width (C) 54 0.798
Calvarial length - face length 29 0.784
Calvarial length - maximum breadth 39 0.770
Muzzle width ectomolare - palate width (C) 54 0.764
Face length - nasal height 35 0.760
Maximum  width (C) - face length 43 0.758
 

APPENDIX 1.

Generalized baboon morphology illustrating measurements taken in this study.

appendix1

APPENDIX 2.

Raw data for fossils used in this study. A single set of parentheses indicates that the measurement was estimated with a high degree of confidence, and the values were used in the analyses. A double set of parentheses indicates that the measurement was estimated with a low degree of confidence, and the values were not used in the analyses. (Appendixes 2-8 available as spreadsheets in zipped file.)

APPENDIX 3.

Raw data for the extant papionins used in this study. (Appendixes 2-8 available as spreadsheets in zipped file.)

APPENDIX 4.

Descriptive statistics for the cranial measurements taken in this study, by fossil species. (Appendixes 2-8 available as spreadsheets in zipped file.)

APPENDIX 5.

Full ANOVA detailing genus comparisons for raw cranial measurements across fossil genera. Shaded cells are significant at p < 0.05. (Appendixes 2-8 available as spreadsheets in zipped file.)

APPENDIX 6.

ANOVA detailing extant genus comparisons for geometric mean scaled data for a subset of cranial measurements. Shaded cells are significant at p < 0.05, n = 81. (Appendixes 2-8 available as spreadsheets in zipped file.)

APPENDIX 7.

ANOVA detailing fossil genus comparisons for geometric mean scaled data for a subset of cranial measurements. Shaded cells are significant at p < 0.05, n = 25. (Appendixes 2-8 available as spreadsheets in zipped file.)

APPENDIX 8.

Full correlation matrix detailing fossil correlations and sample size for the 17 geometric mean scaled cranial measurements. Yellow highlighted cells are significant at p < 0.0004, and grey shaded cells give sample sizes for each measurement pair. (Appendixes 2-8 available as spreadsheets in zipped file.)

 

 

author1Tesla A. Monson. Department of Integrative Biology, University of California, Berkeley, 3040 Valley Life Sciences Building #3140, Berkeley, CA 94720, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.

Tesla Monson is a Ph.D. candidate in the Department of Integrative Biology at the University of California, Berkeley. Her research focuses on the evolution of mammalian craniodental variation, the evolution of body size and life history traits in mammals, and the interpretation of mammalian species variation in the fossil record. Tesla's dissertation addresses the relationship between phylogeny, life history, and dental eruption sequence in mammals. Tesla also hosts and produces The Graduates on KALX 90.7FM, a talk radio show dedicated to science education and outreach, and diversity in STEM.

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author2Marianne F. Brasil. Department of Integrative Biology, University of California, Berkeley; Human Evolution Research Center, 3040 Valley Life Sciences Building #3140, Berkeley, CA 94720, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.

Marianne Brasil is a Ph.D. candidate in the Department of Integrative Biology at the University of California, Berkeley. Marianne's research interest is in mammalian dental and skeletal variation, particularly how variation is patterned and interpreted in the fossil record. Marianne's dissertation research focuses on early modern human skeletal remains from the Middle Awash area of Ethiopia, and she is an active member of the Middle Awash research project.

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author3Dominic J. Stratford. School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein 2000, Johannesburg, South Africa. This email address is being protected from spambots. You need JavaScript enabled to view it.

Dominic Stratford is research director of the Sterkfontein Caves and senior lecturer of geoarchaeology at the University of the Witwatersrand, Johannesburg, South Africa. Dominic's research interests focus on the development and application of multidisciplinary analyses to help refine contextual control of palaeoanthropological and archaeological assemblages during and after their excavation. As a consequence of this focus, Dominic's interests cover a range of earth and biological sciences from vertebrate morphology to sediment micromorphology. Dominic is involved in field work in several areas of South Africa and Namibia spanning the late Pliocene to Holocene.

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author4Leslea J. Hlusko. Department of Integrative Biology, University of California, Berkeley; Human Evolution Research Center, 3040 Valley Life Sciences Building #3140, Berkeley, CA 94720, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.

Leslea Hlusko's research explores the genetic underpinnings of skeletal variation and how this has evolved through time as seen in the fossil record. The focus is on mammalian evolution, with an emphasis on primates. Lab methods span from quantitative genetic analyses to gene expression studies. Leslea has co-directed field paleontology projects in Kenya and Tanzania, and participates in field projects in Ethiopia and Turkey. Her paleontological research is focused on mammalian evolution in the Neogene of Africa and Eurasia. She is currently an Associate Professor of Integrative Biology at the University of California Berkeley.