Last class - San Jose State University following is a description of Au. sediba: Order Primates...

Last class

• What species of hominid are found in the early Pliocene?

• Where are they found?

• What are their distinguishing anatomical characteristics?

• How do the Australopithecines differ from the possible hominids?

Tuesday, April 19, 2011

Taxonomy

• Superfamily: Hominoidea

• Family: Hominidae

• Subfamily: Homininae

• Tribe: Australopithecini


Cast of CharactersOrrorin tugenensis

Sahelanthropus tchadensisArdipithecus kadabbaArdipithecus ramidus

Australopithecus anamensisAustralopithecus afarensisKenyanthropus platyops

Australopithecus bahrelghazali


Australopithecines

• What are the common characteristics of the early Australopithecines?

• How do the species differ from one another?

• When does each fall in time and space?

• What are the possible phylogenies of these species?


Australopithecus afarensis• 3.9-2.9 mya

• Short, broad pelvis

• tilted femurs

• In-line big toe

• Sagittal crest

• Sexually dimorphic

• Small bodied

• Small brain

5


6



7

• 3.5-3.0 mya

• Western africa - Chad

• Same as A. afarensis?


Kenyanthropus platyops

8


Kenyanthropus lateral

9


A. afarensis and K. platyops

10


Kenyanthropus platyops

• 3.5 mya

• Flat face

• Small molars

• Australopithecus? Even A. afarensis?

11


12

Evolutionary Relationships


13


14


Pliocene HominidsAustralopithecus anamensisAustralopithecus afarensisKenyanthropus platyops


Early

Australopithecus africanusAustralpithecus gahri

Australopithecus sediba

Gracile RobustAustralopithecus (P.) aethiopicus

Australopithecus (P.) boiseiAustralopithecus (P.) robustus


Later AustralopithecinesGracile Australopithecines

Australopithecus gahri Australopithecus africanusAustralopithecus sediba

Robust AustralopithecinesAustralopithecus aethiopicus

Australopithecus boiseiAustralopithecus robustus


The Robust Australopithecines• AKA Paranthropus

• Hard object feeding

• Sagittal crest

• Large cheek teeth

• Flared zygomatic arch

• Dished Face

• Extreme postorbital constriction

• Woodland and open woodland habitat


Robust and gracile


Kenyanthropus - robust?


Australopithecus aethiopicus2.7-2.3 mya


Australopithecus boisei2.3-1.3 mya


Australopithecus robustus2-1 mya


Gracile Australopithecines

• Slight brain size increase

• Rounded Vault

• No crests

• Less projecting face

• Bipedal anatomy

• 3.5-<2.0 mya


Australopithecus gahri2.5 mya


Taung


Australopithecus africanus3-2.4 mya


Reconstruction



• dates to right around 1.9 mya - no older than that

• brain size (95% adult size) ~ 420 cc

• maximum height 1.3 m

• smaller teeth and cheekbones than A. africanus

• longer legs and pelvic changes more like Homo



Australopithecus sediba: A NewSpecies of Homo-Like Australopithfrom South AfricaLee R. Berger,1,2* Darryl J. de Ruiter,3,1 Steven E. Churchill,4,1 Peter Schmid,5,1Kristian J. Carlson,1,6 Paul H. G. M. Dirks,2,7 Job M. Kibii1

Despite a rich African Plio-Pleistocene hominin fossil record, the ancestry of Homo and its relationto earlier australopithecines remain unresolved. Here we report on two partial skeletons with anage of 1.95 to 1.78 million years. The fossils were encased in cave deposits at the Malapa site inSouth Africa. The skeletons were found close together and are directly associated with craniodentalremains. Together they represent a new species of Australopithecus that is probably descendedfrom Australopithecus africanus. Combined craniodental and postcranial evidence demonstratesthat this new species shares more derived features with early Homo than any other australopithspecies and thus might help reveal the ancestor of that genus.

The origin of the genus Homo is widelydebated, with several candidate ancestorsbeing proposed in the genus Australopith-

ecus (1–3) or perhaps Kenyanthropus (4). Theearliest occurrence of fossils attributed to Homo(H. aff.H. habilis) at 2.33 million years ago (Ma)in Ethiopia (5) makes it temporally antecedent toall other known species of the genus Homo.Within early Homo, the hypodigms and phylo-genetic relationships between H. habilis andanother early species, H. rudolfensis, remainunresolved (6–8), and the placement of thesespecies within Homo has been challenged (9).H. habilis is generally thought to be the ancestorof H. erectus (10–13), although this might bequestioned on the basis of the considerabletemporal overlap that existed between them(14). The identity of the direct ancestor of thegenusHomo, and thus its link to earlier Australo-pithecus, remains controversial. Here we describetwo recently discovered, directly associated, par-tially articulated Australopithecus skeletons fromthe Malapa site in South Africa, which allow usto investigate several competing hypotheses re-garding the ancestry of Homo. These skeletonscannot be accommodated within any existingfossil taxon; thus, we establish a new species,Australopithecus sediba, on the basis of a com-

bination of primitive and derived characters of thecranium and postcranium.

The following is a description of Au. sediba:Order Primates Linnaeus 1758; suborder Anthro-poidea Mivart 1864; superfamily HominoideaGray 1825; family Hominidae Gray 1825; genusAustralopithecus DART 1925; species Australo-pithecus sediba sp. nov.

Etymology. The word sediba means “foun-tain” or “wellspring” in the seSotho language.

Holotype and paratype. Malapa Hominin1 (MH1) is a juvenile individual represented bya partial cranium, fragmented mandible, and par-tial postcranial skeleton that we designate asthe species holotype [Figs. 1 and 2, supportingonline material (SOM) text S1, figs. S1 and S2,and table S1]. The first hominin specimen re-covered from Malapa was the right clavicle ofMH1 (UW88-1), discovered by Matthew Bergeron 15 August 2008. MH2 is an adult individualrepresented by isolated maxillary teeth, a partialmandible, and partial postcranial skeleton that wedesignate as the species paratype. AlthoughMH1is a juvenile, the second molars are alreadyerupted and in occlusion. Using either a humanor an ape model, this indicates that MH1 hadprobably attained at least 95% of adult brain size(15). Although additional growth would haveoccurred in the skull and skeleton of thisindividual, we judge that it would not haveappreciably altered the morphology on whichthis diagnosis is based.

Locality. The two Au. sediba type skeletonswere recovered from the Malapa site (meaning“homestead” in seSotho), situated roughly 15 kmNNE of the well-known sites of Sterkfontein,Swartkrans, and Kromdraai in Gauteng Province,South Africa. Detailed information regardinggeology and dating of the site is in (16).

RESEARCHARTICLES

1Institute for Human Evolution, University of the Witwatersrand,Private Bag 3, Wits 2050, South Africa. 2School of Geosciences,University of theWitwatersrand, Private Bag 3, Wits 2050, SouthAfrica. 3Department of Anthropology, Texas A&M University,College Station, TX 77843, USA. 4Department of EvolutionaryAnthropology, Box 90383, DukeUniversity, Durham, NC 27708,USA. 5Anthropological Institute and Museum, University ofZürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.6Department of Anthropology, Indiana University, Bloomington,IN 47405, USA. 7School of Earth and Environmental Sciences,James Cook University, Townsville, Queensland 4811, Australia.

*To whom correspondence should be addressed. E-mail:[email protected]

Fig. 1. Craniodental elements of Au. sediba. UW88-50 (MH1) juvenile cranium in (A) superior, (B)frontal, and (C) left lateral views. (D) UW88-8 (MH1) juvenile mandible in right lateral view, (E)UW88-54 (MH2) adult mandible in right lateral view, (F) UW88-8 mandible in occlusal view, (G)UW 88-54 mandible in occlusal view, and (H) UW 88-50 right maxilla in occlusal view (scale barsare in centimeters).

www.sciencemag.org SCIENCE VOL 328 9 APRIL 2010 195



Diagnosis. Au. sediba can be distinguishedfrom other species of Australopithecus by acombination of characters presented in Table 1;comparative cranial measures are presented inTable 2. A number of derived characters separateAu. sediba from the older chronospecies Au.anamensis and Au. afarensis. Au. sediba exhibitsneither the extreme megadontia, extensive cra-nial cresting, nor facial prognathism of Au. garhi.The suite of derived features characterizingAu. aethiopicus, Au. boisei, and Au. robustus,in particular the pronounced cranial muscle mark-ings, derived facial morphology, mandibularcorpus robusticity, and postcanine megadontia,are absent in Au. sediba. The closest morpholog-ical comparison for Au. sediba is Au. africanus,as these taxa share numerous similarities in thecranial vault, facial skeleton, mandible, andteeth (Table 1). Nevertheless, Au. sediba can bereadily differentiated from Au. africanus onboth craniodental and postcranial evidence.Among the more notable differences, we ob-serve that although the cranium is small, thevault is relatively transversely expanded withvertically oriented parietal walls and widelyspaced temporal lines; the face lacks the pro-

nounced, flaring zygomatics of Au. africanus;the arrangement of the supraorbital torus, naso-alveolar region, infraorbital region, and zy-gomatics result in a derived facial mask; themandibular symphysis is vertically oriented witha slight bony chin and a weak post-incisive pla-num; and the teeth are differentiated by theweakly defined buccal grooves of the maxillarypremolars, the weakly developed median lingualridge of the mandibular canine, and the smallabsolute size of the postcanine dentition. Theseexact differences also align Au. sediba with thegenusHomo (see SOMtext S2 for hypodigms usedin this study). However, we consider Au. sedibato be more appropriately positioned withinAustralopithecus, based on the following cranio-dental features: small cranial capacity, pronouncedglabelar region, patent premaxillary suture,moderate canine jugum with canine fossa, smallanterior nasal spine, steeply inclined zygomati-coalveolar crest, high masseter origin, moderatedevelopment of the mesial marginal ridge of themaxillary central incisor, and relatively closelyspaced premolar and molar cusps.

Postcranially, Au. sediba is similar to otheraustralopiths in its small body size, its relatively

long upper limbs with large joint surfaces, andthe retention of apparently primitive charac-teristics in the upper and lower limbs (table S2).Au. sediba differs from other australopiths, butshares with Homo a number of derived featuresof the os coxa, including increased buttressing ofthe ilium and expansion of its posterior portion,relative reduction in the distance between thesacroiliac and hip joints, and reduction of dis-tance from the acetabulum to the ischial tuberos-ity. These synapomorphies with Homo anticipatethe reorganization of the pelvis and lower limb inH. erectus and possibly the emergence of moreenergetically efficient walking and running inthat taxon (17). As with the associated cranialremains, the postcranium of Au. sediba is definednot by the presence of autapomorphic featuresbut by a unique combination of primitive andderived traits.

Cranium. The cranium is fragmented andslightly distorted. The minimum cranial capacityof MH1 is estimated at 420 cm3 (SOM text S4).The vault is ovoid, with transversely expanded,vertically oriented parietal walls. The widelyspaced temporal lines do not approach themidline. Postorbital constriction is slight. Theweakly arched supraorbital torus is moderatelydeveloped and laterally extended, with sharplyangled lateral corners and a weakly definedsupratoral sulcus. A robust glabelar region isevident, with only a faint depression of thesupraorbital torus at the midline. The frontalprocess of the zygomatic faces primarily laterallyand is expanded medially but not laterally. Thezygomatic prominence does not show antero-lateral expansion. The zygomatics are weaklyflared laterally, resulting in an uninterruptedfrontal profile of the facial mask that is squaredsuperiorly and tapered inferiorly. The zygomat-icoalveolar crests are long, straight, and steep-ly inclined, resulting in a high masseter origin.The root of the zygomatic begins at the anteriormargin of M1. The nasal bones are widenedsuperiorly, become narrowest about one-thirdof the way down, and flare to their widest extentat their inferior margin. The nasal bones areelevated as a prominent ridge at the internasalsuture, with an increasingly anterior projectioninferiorly. The bone surface of the maxilla re-treats gently away from the nasal aperture lat-erally, resulting in an everted margin of thesuperolateral portion of the aperture relative tothe infraorbital region. The inferolateral portionof the nasal aperture becomes bluntly rounded.The infraorbital region is slightly convex (18)and is oriented at an approximately right angleto the alveolar plane. There is a trace of a pre-maxillary suture near the superolateral marginof the nasal aperture. Prominent canine jugadelineate moderately developed canine fossae.Anterior pillars are absent. The inferior marginof the nasal aperture is marked by a steppednasal sill and a small but distinct anterior nasalspine. The subnasal region is straight in the cor-onal plane and only weakly projecting relative

Fig. 2. Associated skeletal elements of MH1 (left) and MH2 (right), in approximate anatomical position,superimposed over an illustration of an idealized Au. africanus skeleton (with some adjustment fordifferences in body proportions). The proximal right tibia of MH1 has been reconstructed from a naturalcast of the proximal metaphysis.

9 APRIL 2010 VOL 328 SCIENCE www.sciencemag.org196

RESEARCH ARTICLES


Contemporaneous?


Brain and body sizesSahelanthropus ~350cc

A. afarensis 29 kg f / 45 kg m ~375-550A. africanus 30 kg f / 40 kg m ~530

A. aethiopicus ~415A. sediba ~420A. boisei 34 kg f / 49 kg m ~530 cc

A. robustus 32 kg f / 40 kg m ~590 ccHomo habilis 32 kg f / 52 kg m 500-800 cc


Hominin characteristicsand time frame


Traditional Hominin phylogenies


Phylogenies?


A. afarensis?


Robust Australopithecus?


Defining Homo

• Rasmussen: Primate genus containing species of relatively small-toothed, big-brained, stone-tool-making hominids

• Walker: relatively large brain cases, completely modern limb proportions, and relatively small teeth

• Wolpoff: expanded cranial capacity, reduced canine size, precision grip


Homo habilis


Australopithecus v. Homo habilis


Homo

• brain size greater than 500 cc

• smaller, less prognathic face

• smaller teeth than the australopithecines

• more efficient bipedalism


Homo species

• Homo habilis

• Homo erectus

• Homo rudolfensis

• Homo ergaster

• Homo floresiensis

• Homo heidelbergensis

• Homo rhodesiensis

• Homo antecessor

• Homo neandertalensis

• Homo sapiens


Homo habilis


Homo rudolfensis


Homo rudolfensis

• Homo habilis or something different?

• larger body than. H. habilis

• larger brain than H. habilis

• but smaller EQ

• bigger teeth than H. habilis


Savanna-Woodland


Olduwan Chopper


Last class - San Jose State University following is a description of Au. sediba: Order Primates...

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