Sahabi Eurygnathohippus Feibeli: Its Systematic, Stratigraphic, Chronologic and Biogeographic Contexts

Home , Cormohipparion, Cremohipparion, European land mammal age, Eurygnathohippus, MN zonation, Nannippus

5LYLVWD,WDOLDQDGL3DOHRQWRORJLDH6WUDWLJUD¿D (Research in Paleontology and Stratigraphy) vol. 126(2): 561-581. July 2020

SAHABI EURYGNATHOHIPPUS FEIBELI: ITS SYSTEMATIC, STRATIGRAPHIC, CHRONOLOGIC AND BIOGEOGRAPHIC CONTEXTS

RAYMOND L. BERNOR 1,2, NOEL T. BOAZ3, OMAR CIRILLI4,5*, MOFTAH H. EL-SHAWAIHDI 3,6 & LORENZO ROOK5*

1College of Medicine, Department of Anatomy, Laboratory of Evolutionary Biology, 520 W St. N.W., Washington D.C. 20059. Email: [email protected] 2Human Origins Program, Department of Anthropology, Smithsonian Institution, Washington D.C. 3International Institute for Human Evolutionary Research, Integrative Centers for Science and Medicine, 12 Starling Avenue, Martinsville, Virginia 24112. Email: [email protected] 4Dottorato di Ricerca in Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy. E-mail: [email protected] 5Dipartimento di Scienze della Terra, Paleo[Fab]Lab, Università degli Studi di Firenze, Via G. La Pira 4, 50121 Firenze, Italy. (PDLOORUHQ]RURRN#XQLÀLW 6Department of Earth Sciences, University of Benghazi, Benghazi, Libya; Email: [email protected] *Corresponding Author

To cite this article: Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L. (2020) - Sahabi Eurygnathohippus feibeli: its systematic, stratigraphic, chronologic and biogeographic contexts. Riv. It. Paleontol. Strat., 126(2): 561-581.

Keywords: Eurygnathohippus feibeli; Origins; Paleobiogeographic history; Africa; late Miocene. . Abstract. Sahabi, Libya is an important latest Miocene locality having yielded an extensive paleobotanical and vertebrate fauna. Amongst the fossil mammals there occurs an extensive, species diverse record of hipparionine horses. We develop here a complete record of Sahabi Eurygnathohippus feibeli now based on dental and postcranial material, LQFRPSDULVRQWRRWKHUHTXLGVIURPODWH0LRFHQHHTXLGVIURP(XURSH:HVW$VLDDQG$IULFD:HÀQGWKDWE. feibeli is the earliest recognized species of the predominantly African clade Eurygnathohippus, that its biogeographic range was Kenya, Ethiopia, Libya and Morocco, it ranged between 7.0 and 5.7 Ma and that it had deep-time evolutionary roots H[WHQGLQJEDFNWRÀUVWRFFXUULQJ2OG:RUOGKLSSDULRQV:HIXUWKHUÀQGWKDWEurygnathohippus was restricted to Africa until a more advanced member of the clade extended its range into the Indian Subcontinent during the late Pliocene, ca. 3.6-2.6 Ma.

INTRODUCTION Scott 2003; Bernor et al. 2008, 2012). Previous contributions to our understanding of Eurygnathohippus The genus Eurygnathohippus has been reported feibeli has largely been restricted to its derived postcra- from the late Miocene – Pleistocene of Africa (Ber- nial skeleton, with the exception of the partial skull nor & Harris 2003; Bernor & Kaiser 2006; Bernor et of E. feibeli from Ekora, Kenya (Bernor & Harris al. 2005, 2010; Cirilli et al. 2020). The genus’ appear- 2003). This contribution integrates additional post- ance in Eurasia is limited to the Indian late Pliocene crania and dental morphology into our recognition (Jukar et al. 2019). The oldest recognized member of of Eurygnathohippus feibeli and engages a more com- this genus - Eurygnathohippus feibeli - has been reported prehensive comparative analysis of postcrania with from Lothagam, Kenya (Bernor & Harris 2003), the Western Eurasian and Africa localities yielding the late Miocene of the Middle Awash, Ethiopia (Bernor genera Cormohipparion, Hipparion s.s., Cremohipparion, & Hailie Selassie 2009), and Sahabi, Libya (Bernor & Sivalhippus and Eurygnathohippus. We recognize the basal evolutionary status of Central European Hip- Received: March 5, 2020; accepted: June 19, 2020 potherium primigenium (Bernor et al. 1997, 2017), Turk- 562 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

Fig. 1 - Geographical Locator Map: A) Akkasdagi; C) Calta; E) Eppelsheim; G) Lothagam; H) Hoewenegg; I) Pikermi; K) Kurutlu; U) Mt. Lube- ron; M) Maragheh; N) Sinap & Esme Acakoy; O) Samos; P) Potwar Plateau; Q) Salo- niki; S) Sahabi; W) Awash; Y) Corak Yerler.

Locality Country Age Ma Symbol and uncover morphological pathways in dental and Akkasdagi Turkey 7.1 A postcranial anatomy of Eurygnathohippus and other Calta Turkey 4.0 C hipparionine lineages. Figure 1 is a geographical loca- Eppelsheim Germany 10.0 E tor map of the localities from which our sample is Lothagam Kenya 7.0-5.0 G drawn. These include: the Potwar Plateau (P), Paki- Hoewenegg Germany 10.3 H stan; Hoewenegg (H) and Eppelsheim (E), Germany; Pikermi Greece 8.0 I Mt. Luberon (U), France; Pikermi (I), Saloniki (Q) Kurutlu Turkey late Miocene K and Samos (O), Greece; Maragheh (M), Iran; Sinap Mt. Luberon France 8.0-7.0 U and Esme Acakoy (N), Kurutlu (K), Corak Yerler Maragheh Iran 8.9-7.4 M (Y), Akkasdagi (A) and Calta (C), Turkey; Sahabi (S), Sinap & Esme A. Turkey 10.8-9.0 N Libya; Middle Awash (W), Ethiopia; Lothagam (G), Samos Greece 8.3-7.0 O Kenya. The symbols corresponding to localities (in Potwar Plateau Pakistan 10.8-7.0 P parentheses) are included in Table 1. Saloniki Greece 8.0-7.0 Q Sahabi Libya 7.0-6.7 S Awash Ethiopia 6.0-5.6 W SYSTEMATIC CONVENTIONS Corak Yerler Turkey late Miocene Y

Tab. 1 - Localities and ages analysed in Bivariate Plots. :HIROORZFKDUDFWHUL]DWLRQVDQGGHÀQLWLRQVIRU hipparionine horses recently provided in Bernor et al. (1996, 1997, 2010, 2016). Hipparion monographs ish Cormohipparion sinapensis (Bernor et al. 2003) and by Gromova (1952) and Gabunia (1959) are cited af- Algerian “Cormohipparion” africanum (Bernor & White ter the French and English translations. The taxon 2009) in our statistical and morphological analyses Hipparion has been applied in a variety of ways by Sahabi Eurygnathohippus feibeli 563

GLIIHUHQWDXWKRUV:HXWLOL]HWKHIROORZLQJGHÀQLWLRQV nor et al. (2004, 2005, 2010, 2013), Gilbert & Bernor in this work: (2008), Bernor & Haile Selassie (2009), and Bernor & Hipparionini - a tribe of Equidae with an White (2009) have compared African hipparions to isolated protocone on maxillary premolar and mo- an extensive series of Late Miocene-Pleistocene Eur- lar teeth and, as far as known, tridactyl feet, includ- asian and African assemblages. Bernor & Sun (2015) ing species of the following genera: Cormohipparion, have recently reviewed cheek tooth ontological stages Neohipparion, Nannippus, Pseudhipparion, Hippotherium, in Chinese Plesiohipparion and Proboscidipparion. Cremohipparion, Hipparion, Sivalhippus, Baryhipparion, In various studies Eisenmann (see Eisenmann Shanxihippus, Eurygnathohippus (= a senior synonym 1995 for a comprehensive summary) has used log10 of Stylohipparion), Proboscidipparion and Plesiohipparion. ratio diagrams to evaluate differences in hipparion These lineages have recently been reviewed by Qiu metapodial proportions as a basis for recognizing et al. (1988), Bernor & White (2009), Bernor et al. taxa and their evolutionary relationships. Bernor et (2010, 2013, 2014), Armour-Chelu & Bernor (2011), al. (2003), Bernor & Harris (2003), Armour-Chelu & Wolf et al. (2013), Bernor & Sun (2015), Bernor & Bernor (2011) and Bernor et al. (2014, 2016) have Sen (2017). used multiple statistical tests, including univariate, Hipparion s.s. - the nomen is restricted to a spe- bivariate and multivariate statistics as well as log10 FLÀF OLQHDJH RI KLSSDULRQLQH KRUVHV ZLWK WKH IDFLDO ratio diagrams, to evaluate and resolve the alpha sys- fossa positioned dorsally high on the face (MacFad- tematics of hipparionine horses. Bernor et al. (2005) den 1980, 1984; Woodburne & Bernor 1980; Wood- used log10 ratio diagrams together with multivariate burne et al. 1981; MacFadden & Woodburne 1982; VWDWLVWLFVWRHYDOXDWHPHWDSRGLDODQGÀUVWSKDODQJHDO Bernor 1985; Bernor & Hussain 1985; Bernor & evidence for postcranial evolution in Ethiopian hip- Tobien 1989; Bernor et al. 1996, 2016; Woodburne parions. We incorporate these previously used meth- %HUQRU·VGHÀQLWLRQGHSDUWVIURPVRPHLQYHVWL- odologies in this work. Our statistical analyses use gators in not recognizing North American species of the skeletal population from Hoewenegg (Hegau, Hipparion s.s. Bernor (1985). southern Germany, 10.3 Ma; Bernor et al. 1997) for “Hipparion” - several distinct and separate lin- FDOFXODWLQJFRQÀGHQFHHOOLSVHVXVHGLQELYDULDWH eages of Old World hipparionine horses once con- plots, and log10 mean standard values for all log10 sidered to be referable to the genus Hipparion (re: ratio diagrams for 1PHIII MCIII and MTIII. Bernor et al. 1996; 2010). We emphasize here the Sahabi measurements were taken by R.L. Ber- QHHGWRDYRLGFRQIXVLRQRI ZHOOGHÀQHGKLSSDULRQLQH nor and O. Cirilli. Comparative measurements were lineages with poorly characterized taxa of “Hippa- taken from Bernor’s equid database which will be rion” sensu lato. published on the NSF sponsored FuTRES website Hippotherium - a discrete genus of Western (https://futres.org/) in 2021. Analyses of the Sa- Eurasian hipparionine horses known from Central habi and other African and Eurasian specimens (re: Europe, Italy, Greece, Turkey and Ukraine. Species Table 1) include: hipparion bivariate plots of MCIII, belonging to this genus include H. primigenium, H. in- MTIII and 1PHIII. All of these skeletal elements are trans, H. microdon, H. kammerschmittae, H. malpassii, H. clearly differentiated with the exception of 1PHIII. brachypus and perhaps H. giganteum (re: Bernor et al. While anterior and posterior 1PHIII can be clearly 2011). differentiated in living Equus, the same cannot be said for all hipparions (see, e.g., Wolf et al. 2013). The Hoewenegg hipparion skeletons were found in METRIC PROCEDURES articulation and thus the anterior versus the posterior 1PHIII are known. However, the statistical differ- Measurements are all given in millimeters and ences between these phalanges are minor at best in rounded to 0.1 mm. Measurement numbers (M1, the Hoewenegg sample, which has led us to analyze M2, M3, etc.) refer to those published by Eisenmann all 1PHIII together. Some advanced African hip- et al. (1988) and Bernor et al. (1997) for the skulls SDULRQV PD\ LQ IDFW GLIIHU VLJQLÀFDQWO\ LQ DQWHULRU and postcrania. Tooth measurement numbers refer versus posterior 1PHIII dimensions (Bernor et al. to those published by Bernor et al. (1997) and Bernor 2010). Table 2 provides a list of Sahabi Eurygnatho- & Harris (2003). Bernor & Armour-Chelu (1999), hippus feibeli specimens, their species attributions, Bernor & Harris (2003), Bernor & Scott (2003), Ber- measurements, ages and stratigraphic provenience. 564 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

63(&B,' 63(&,(6 6(; %21( 6,'( $*( 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /2& 81,7 ,633$ Eu. feibeli SK UW 3$ 8 ,633$ Eu. feibeli SK UW 3$ 8 ,633% Eu. feibeli SK OW 3% 8 ,633$ Eu. feibeli SK UW 3$ 8 ,633$ Eu. feibeli SK OW 3$ 8 ,633$ Eu. feibeli SK UW 3$ 8 ,633$ Eu. feibeli SK OW 3$ 8 ,633$ Eu. feibeli SK OW 3$ 8 ,633$ Eu. feibeli DVWUDJDOXV UW ϰϮ͕ϭ ϯϴ͕ϱ Ϯϴ͕ϵ ϯϱ͕ϵ Ϯϲ͕ϭ ϯϮ͕ϵ ϯϰ͕ϭ 3$ 8 ,633$ Eu. feibeli DVWUDJDOXV OW 3$ 8 ,633$ Eu. feibeli DVWUDJDOXV OW 3$ 8 ,633$ Eu. feibeli DVWUDJDOXV UW 3$ 8 ,633$ Eu. feibeli DVWUDJDOXV UW 3$ 8 ,633$ Eu. feibeli FDOFDQHXP UW 3$ 8 ,633$ Eu. feibeli FDOFDQHXP UW 3$ 8 ,633$ Eu. feibeli FDOFDQHXP UW 3$ 8 ,633$ Eu. feibeli FXERLGHXP OW 3$ 8 ,633$ Eu. feibeli FXQHLIRUPH UW 3$ 8 ,633$ Eu. feibeli FXQHLIRUPH UW 3$ 8 ,633% Eu. feibeli PDJQXP UW 3% 78 ,633$ Eu. feibeli PDJQXP UW 3$ 8 ,633$ Eu. feibeli PDJQXP UW 3$ 8 ,633% Eu. feibeli PDQGLEOH OW 3% 8 ,633% Eu. feibeli PDQGLEOH OW 3% 8 ,633$ Eu. feibeli PDQGV\PSK 3$ 8 ,633$ Eu. feibeli PFLLL UW 3$ 8 ,633$ Eu. feibeli PFLLL OW 3$ 8 ,633$ Eu. feibeli PWLL OW 3$ 8 ,633$ Eu. feibeli PWLL UW 3$ 8 ,633$ Eu. feibeli PWLL OW 3$ 8 ,633$ Eu. feibeli PWLL OW 3$ 8 ,633$ Eu. feibeli PWLLL OW 3$ 8 ,633$ Eu. feibeli PWLLL OW 3$ 8 ,633$ Eu. feibeli PWLLL UW 3$ 8 ,633$ Eu. feibeli PWLLL UW 3$ 8 ,633$ Eu. feibeli PWLLL OW 3$ 8 ,633$ Eu. feibeli PWLLL OW 3$ 8 ,633$ Eu. feibeli PWLY UW 3$ 8 ,633$ Eu. feibeli PWLY OW 3$ 8 ,633$ Eu. feibeli QDYLFXODUH UW 3$ 8 ,633$ Eu. feibeli QDYLFXODUH OW 3$ 8 ,633$ Eu. feibeli WLELD UW 3$ 8 ,633$ Eu. feibeli WLELD UW 3$ 8 ,633$ Eu. feibeli WLELD OW 3$ 8 ,633% Eu. feibeli WPP UW 3% 8 ,633 Eu. feibeli WPP UW 3 8 ,633 Eu. feibeli WPP OW 3 8 ,633$ Eu. feibeli WPP UW 3$ 8 ,633$ Eu. feibeli WPP UW 3$ 8 ,633$ Eu. feibeli WPP OW 3$ 8 ,633$ Eu. feibeli WPP UW 3$ 8 ,633$ Eu. feibeli WPP UW 3$ 8 ,633$ Eu. feibeli WPP OW 3$ 8 ,633$ Eu. feibeli WPS OW 3$ 8 ,633$ Eu. feibeli WPS UW 3$ 8 ,633 Eu. feibeli WPS UW 3$ 8 ,633$ Eu. feibeli W[0 OW 3$ 8 ,633$ Eu. feibeli W[0 UW 3$ 8 ,633$ Eu. feibeli W[0 OW 3$ 8 ,633$ Eu. feibeli W[0 OW 3$ 8 ,633$ Eu. feibeli W[0 UW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 UW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633% Eu. feibeli W[3 UW 3% 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 UW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8 ,633$ Eu. feibeli W[3 OW 3$ 8

Tab. 2 - Measurements of Eurygnathohippus feibeli. Sahabi Eurygnathohippus feibeli 565

Abbreviations deposits above the Mio-Pliocene boundary. El-Sha- In this manuscript we use the abbreviation Ma for mega- waihdi et al. (2016) utilized extensive results from annum in the geochronologic time scale. Ages in m.y. are based on radioisotopic or magnetostratigraphic analyses. North Africa localities DGGLWLRQDO ÀHOGZRUN FRUH GULOOLQJ DQG ODERUDWRU\ may be referred to the MN biochronologic time scale (Rook et al. analyses to revise the Sahabi stratigraphy (Fig. 2). 2019). Western Eurasia Vallesian, Turolian, and Ruscinian intervals of 7KHPDMRUHIIHFWRI WKLVUHYLVLRQZDVWRGHÀQHWKH the European land mammal age sequence are commonly termed units (sensu Fahlbusch 1991). upper and lower limits of the Sahabi Formation. Measurement Table Abbreviations. Sex: M = male; F = The unconformity above Unit U2 is now correlated IHPDOH" XQNQRZQ6H[FDQEHGHÀQHGE\WKHVL]HRI DFDQLQHWRRWK with the Messinian-aged down-cutting of the Eo- male being large, female being small. Side: lt. = left; rt. = right. Cranial: sahabi River, yielding a minimum age of the top of IOF = infraorbital foramen; POB = preorbital bar; POF = preorbital IRVVD3RVWFUDQLDO3+,,, ÀUVWSKDODQ[,,, FHQWUDOGLJLW RI HLWKHU Upper Member of the Sahabi Formation of 5.3 ma. WKH DQWHULRU RU SRVWHULRU OLPE ZKLFK DUH GLIÀFXOW WR GLVWLQJXLVK LQ Sediments of the Qarat Weddah Formation, for- most hipparion species; MCIII = metacarpal III; MTIII = metatarsal merly named Member V of the Sahabi Formation, III; MPIII = metapodial III. M1-M38 refers to measurements as de- UHSUHVHQWV WKH WUDQVJUHVVLYH LQÀOOLQJ RI WKH (RVD- scribed by Eisenmann et al. (1988) and Bernor et al. (1997). Statistical plots include abbreviations by locality (Locality Symbols are included KDEL&KDQQHOGXULQJWKHUHÀOOLQJRI WKH0HGLWHU- in Table 1). ranean Basin at the end of the Miocene. Museum Collections Abbreviations. We sample the fol- The former Formation P is now recognized lowing museum and institutional vertebrate collections for this study: AMNH – American Museum of Natural History, New York; ISP as a gypsiferous lagoonal deposit comprising the – International Sahabi Project Collection in Museum of Vertebrate Lower Member of the Sahabi Formation, within Paleontology, University of Benghazi, Libya; MMTT – Muze Melli the Messinian Stage beginning at 7.2 Ma but not Tarikh Tabeie, Tehran; MNHN – Museum National d’Histoire Na- coterminous with the Messinian Salinity Crisis at turelle, Paris; NHMW – Naturhistorisches Museum, Wien; MCZR – Museo Civico di Zoologia, Rome. the end of the stage, 5.3 Ma. Formation P overlies the marine limestone of Formation M, now reliably correlated with the Benghazi Formation and dated to the Tortonian Stage (11.6 – 7.2 Ma; Muftah et al. SAHABI STRATIGRAPHY AND CHRONOLOGY 2008). El-Shawaihdi et al. (2014) dated the Beng- hazi Formation at Sahabi to between 9.6 and 9.0 Sahabi is a latest Miocene locality in northern Ma based on the 87Sr/86Sr isotope analyses of unal- Libya, well known for its celebrated vertebrate fossil tered marine invertebrate fossils plotted against the fauna. In the 1920s and 1930s there was at Sahabi an marine strontium isotopic curve. Calcareous nan- Italian army station and, being on the road to various nofossils recovered from cores into the Benghazi sites into the Libyan Desert, the area was frequently Formation drilled at Sahabi correlate to biozone crossed by caravans and explorers and was visited 11E11DDQGFRQÀUPLWV/DWH0LRFHQH 7RU- by eminent geologists and palaeontologists (Rook tonian) age. Beyer (2008) reported a K-Ar date of $IWHUVHYHUDOGHFDGHVRI QRÀHOGDFWLYLW\DW sedimentary glauconite from the Benghazi Forma- Sahabi, multidisciplinary research teams undertook tion (former Formation M) at Locality P53 which extensive investigations in the area from the middle yielded an age of between 7.7 – 7.5 Ma, but he 1970’s to early 1980’s, and later on since early 2000’s noted that that these sediments may well have been (Boaz et al. 1979, 1987, 2008). redeposited and not representative of the deposit’s The Sahabi Formation was named and de- actual age. scribed by de Heinzelin & El-Arnauti (1987) as one The fossiliferous Upper Member of the Sa- of three formations with an aggregate stratigraphic habi Formation is a package of interbedded layers thickness of over 60 meters outcropping over an of sand and clay laid down by a large, slow-mov- area of some 50 by 30 km (1500 sq. km.). They in- ing Eosahabi River and its related lagoonal and terpreted Formation P, a gypsum-rich layer underly- estuarine facies near the paleo-Gulf of Sirt (Boaz ing the Sahabi Formation to be of Late Miocene 2008). The vertebrate fossil assemblage is surface (Messinian) age. Formation P in turn overlies the -collected within mapped localities with secure marine limestone of Formation M of presumed spatial and stratigraphic control. The Sahabi fossil Middle Miocene age (de Heinzelin & El-Arnauti equid sample derives almost exclusively from one 1987). Correlating Formation P with the Messinian sedimentary unit, Unit U1 of the Upper Member Salinity Event placed the vertebrate fossil-bearing of the Sahabi Formation. Beyer (2008) reported a 566 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

Rook 2019). The age of Sahabi Eurygnathohippus feibeli is therefore estimated to be 6.8 Ma (Boaz et al. 2008) and agrees well with the chronologic range of E. feibeli from Morocco, Ethiopia and Kenya.

STATISTICAL ANALYSIS

Bivariate Plots Bivariate plots will include two parallel sets of plots: one of our entire analytical sample; a second of the Sahabi (S), Middle Awash (W) and Lothagam (G) specimens plotted: all localities with Eurygnatho- hippus feibeli. We analyze 1PHIII, MCIII and MTIII below. The bivariate plots on bones have a 95% ellipse representing the Hoewenegg population standard of Hippotherium primigenium. The array of comparative Hipparion measurements is intended to be heuristic for demonstrating the range of variation in size and proportion of the element/sample com- bination being plotted. Figure 3 plots 1PHIII dimensions of maximum length (M1) versus distal articular width (M7). Most of the sample falls within the Hoewenegg Fig. 2 - Sahabi chronological interpretation and stratigraphic co- FRQÀGHQFHHOOLSVH )LJ$ 7KHUHDUHODUJHU lumn (not to scale) with synopsis of formational subdi- specimens above the ellipse from Pakistan (P), Sa- vision (Heinzelin & El-Arnauti 1987; Muftah et al. 2020), rock units (El-Shawaihdi et al. 2016), and depositional envi- loniki (Q) and Middle Awash (W). A large specimen ronments (El-Shawaihdi et al. 2016). with the widest distal articular dimension is from Calta (C) and is referable to Proboscidipparion heintzi (Bernor & Sen 2017). Smaller specimens are derived magnetized clayey bed in Unit U1 at Locality P28 from Sinap and Esme Acakoy (N), Samos (O), and WKDWKHLQWHUSUHWHGDVDWXIÀWHDQGQHDUZKLFKKH Mt. Luberon (U). These are likely small members of obtained preliminary paleomagnetic results. Muftah the Cremohipparion clade (Bernor et al. 2016). Figure et al. (2013) reported detailed microstratigraphic 3B plots specimens from Lothagam (G), Sahabi (S) and mineralogical analyses of this unit at two Sa- and Middle Awash (W), all within or on the upper habi localities which yielded no minerals of volcanic border of the Hoewenegg ellipse. origin, datable by isotopic analyses, but rather felsic Figure 4 plots MCIII maximum length (M1) minerals consistent with a sedimentary origin from versus distal articular width (M11). Figure 4A plots Precambrian rocks in northeastern Chad. Boaz et many specimens within the Hoewenegg ellipse in- al. (2008) differentiated the U1 mammalian fauna cluding Sinap and Esme Acakoy (N), Maragheh (M), as correlative with the Messinian age while that col- Pikermi (I), Samos (O) and Eppelsheim (E). Above lected by Italian expeditions in the 1930’s was likely the ellipse there are a great number of specimens collected from the younger U-2 unit covered in part from Akkasdagi (A), the longest ones representing by Qarat Weddah Formation (formerly Unit V) and cf. Plesiohipparion longipes (Koufos & Vlachou 2005). Formation Z (Fig. 2). Boaz et al. (2008) estimated There are elongate specimens from Maragheh (M) Sahabi U1’s fauna as being ca. 6.8 ma. This age is referable to cf. Cremohipparion moldavicum (Bernor et consistent with a biostratigraphic age review and al. 1996), Samos (O) and Pikermi (I) referable to biogeographic comparison of late Miocene and Cremohipparion sp. Specimens to the left of the el- (XUDVLDQIDXQDV %HUQRU 5RRN3DQGROÀ lipse include specimens from Saloniki (Q) referable Sahabi Eurygnathohippus feibeli 567

Fig. 3 - 1PHIII maximum length (M1) versus distal articular width Fig. 4 - MCIII maximum length (M1) versus distal articular width (M7); A) entire sample; B) Lothagam (G), Sahabi (S) and (M11). A) entire sample; B) Lothagam (G), Sahabi (S) and Middle Awash (W) only. Middle Awash (W) only. to cf. Hipparion prostylum (Bernor et al. 2016), Mara- to cf. Eurygnathohippus feibeli. The one specimen to gheh (M) cf. Hipparion spp., Pikermi (I) and Akkas- the right of the upper portion of the ellipse from dagi (A) likely representing smaller, slender limbed Lothagam is referable to cf. Sivalhippus turkanensis. Cremohipparion spp. Below the ellipse and to the left The one specimen below the ellipse from Sahabi is the smallest specimens are derived from Samos (O) referable to cf. Cremohipparion small. and Maragheh (M) (cf. Cremohipparion aff. matthewi), Figure 5A plots data on MTIII maximum Sinap (N), Sahabi (S) (cf. Cremohipparion) and Paki- length (M1) versus distal articular width (M11). stan (P) (“Hipparion” sp.). Figure 4B plots two spec- Again, there is a great density of specimens plot- imens above the Hoewenegg ellipse and to the left: ting within the ellipse from Maragheh (M), Pikermi Middle Awash (W) and Lothgam (G) likely referable (I), Samos (O), Pakistan (P), and Sinap and Esme 568 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

specimens of large Sivalhippus sp. from Pakistan (P), Sivalhippus turkanensis from Lothagam (G) and large cf. Hippotherium brachypus from Samos (O). The smallest specimens referable to cf. Cremohippa- rion matthewi are found from Samos (O) and Mara- gheh (M). The small specimen from Pakistan (P) is referable to “Hipparion” sp. Figure 5B includes two MTIII specimens from Sahabi (S), one within the ellipse referable to cf. “Hipparion” large and one to the left of the ellipse that is referable to Eurygna- thohippus feibeli.

Log10 Ratio Analyses Figure 6A and B are log10 ratio diagrams of 1PHIII. Figure 6A compares Sahabi specimens with specimens from Lothagam, Pikermi, Sinap, Langebaanweg and Tizi N’Tadderht specimens. Bernor et al. (2003) recognized a primitive species of Cormohipparion sinapensis from the oldest hipparion bearing horizons at Sinap and Esme Acakoy, Turkey (CsinMean). The Cormohipparion sinapensis log10 ratio exhibits an elongate shaft (M1) and slender (M3) and relatively deep midshaft (M4), narrow proximal articular depth (M6) compared to the Hoewenegg standard. The trajectory of Sinap Cormohipparion sinapensis 1PHIII is shared with Cremohipparion matthewi (Cr.matt), Lothagam Eu- rygnathohippus feibeli, Pikermi Cremohipparion mediterraneum and Sahabi specimen ISP32P25B referable to cf. Eurygnathohippus feibeli. Three larger specimens include Lothagam Mean, the Sahabi MCZR- PV2010.0037 referable to cf. Sivalhippus turkanensis, and the Langebaanweg Mean of Eurygnathohippus hooijeri (Bernor and Kaiser 2006). Figure 6B replots Lothagam cf. Sivalhippus turkanensis Mean, Sinap Cormohipparion sinapensis, European Cremohipparion Fig. 5 - MTIII maximum length (M1) versus distal articular width (M11). A) entire sample; B) Sahabi (S) only. matthewi MEAN, Lothagam Eurygnathohippus feibeli and the Middle Awash late Miocene sample (ALA, BIK, JAB, KAR, DID, ALA) data. JAB-VP1-1 is Acakoy (N). There are many specimens above the the oldest 1PHIII in the Middle Awash sample and ellipse from Akkasdagi (A) which include cf. Plesio- plots very closely with C. sinapensis and Eurygnatho- hipparion longipes and Samos (O) that likely include hippus feibeli from Lothagam. The remaining Middle large species of Cremohipparion ?proboscideum. The Awash specimens, ALA-VP-2-26, KAR-VP-4/3, longest MTIII is from Calta (C), and has been re- BIK-VP-1-3 and DID-VP-1-82 vary slightly from ferred to Plesiohipparion cf. longipes by Bernor & Sen Lothagam Eurygnathohippus feibeli and JAB-VP-1-1 (2017). To the left of the ellipse are slender hip- being slightly more robust and KAR-VP-4/3 is the parions from Maragheh (M), Saloniki (Q), and Mt. longest 1PHIII in the sample. Luberon (U) which include a mixture of Hipparion Figure 7A and B are log10 ratio diagrams cf. prostylum, Cremohipparion moldavicum, and Cremo- of MCIII. Figure 7A includes two primitive MC- hipparion matthewi. To the right of the ellipse are III samples: Cormohipparion sinapensis (Csin) from Sahabi Eurygnathohippus feibeli 569

Fig. 6 - 1PHIII log10 ratio Diagrams. A) 1PHIII Sahabi and other Late Miocene European and African Hipparions log10 ratio compared to Ho. Log10 MEAN, Sahabi is ISP2P111A and ISP32P25B and MCZRPV2010.0037; Lothagam is Sturk (Sivalhip- pus turkanensis), Eu. feibeli is Lothagam mean of Eurygna- thohippus feibeli, Cr.med is Pi- kermi Cremohipparion mediterraneum Mean measurements; Cr.matt_Mean is Mean measurements on Cremohipparion matthewi, Csin_Mean is mean measurements on Sinap & Esme Acakoy Cormohippa- rion sinapensis, Eu.hooijeri_ MEAN is the mean measurements on Langebaaneweg Eurygnathohippus hooijeri. B) 1PHIII Lothagam, European and Middle Awash log10 ratio compared to Ho. log10 MEAN, Sturk Lothagam Mean, Eu.feibeli Lothagam Mean, Cr.med_Pikermi Mean, Middle Awash localities including ALA, BIK, JAB, KAR, DID, ALA (all between 6 and 5.4 Ma), Cr.matt_MEAN and Csin_ Mean.

Sinap and Esme Acakoy and “Cormohipparion” af- with much exaggerated midshaft slenderness (M3) ricanum (Cafr, MNHN1951-9-5Type) from Bou and more slender build but elongate (M1). In Fig- +DQLÀD $OJHULD %HUQRU :KLWH 7KH ure 7B Middle Awash AMW-VP-1-15 and AME- log10 proportions of these two taxa are virtually VP- 1/175 are very similar to the primitive Cor- identical and exhibit narrowing of the midshaft mohipparion sinapensis MCIII log10 trajectory except (M3) with relatively deeper keel (M4) character- for a slightly elevated distal suprarticular tubercle istic of the earliest Old World hipparions, and diameter (M10) permitting a referral to cf. Euryg- distinction from Central European Hippotherium nathohippus feibeli. Lothagam Sivalhippus turkanensis primigenium. Lothagam Eurygnathohippus feibeli (Eu. is substantially larger and more robustly built. feiLothMean), Langebaanweg Eurygnathohippus Figure 8 includes MTIII log10 comparisons hooijeri and Pikermi Cremohipparion mediterraneum all of primitive hipparions in comparison to Sahabi, are remarkably similar to the primitive Old World European and African specimens following the de- Cormohipparion condition. Sahabi IPS82P17A and scription of 1PHIII and MCIII above. Figure 8A ISP25P26A are also similar to Lothagam and the shows once again that Cormohipparion sinapensis and other primitive taxa and referable to cf. Eurygna- “Cormohipparion” africanum have slender and rela- thohippus feibeli. Sahabi IPS27P25B is very similar tively deep midshafts compared to the Hoewenegg to Samos Cremohipparion matthewi and is extremely standard, the so-called “Esme Acakoy Effect” of slender in its midshaft but generally has the same Bernor et al. (2003). Cremohipparion mediterraneum log10 trajectory as the primitive Cormohipparion but and Sahabi ISP67P16A cf. Eurygnathohippus feibeli 570 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

Fig. 7 - MCIII log10 ratio Diagrams. A) Metacarpal III Sahabi, Lothagam, European and African Hip- parions, log10 ratio, Ho Std. – abbreviations as in Figure 6A. B) Metacarpal III Sahabi, Lothagam, European, Middle Awash and African Hipparions, log10 ratio, Ho. Std. AME and AMW Middle Awash Localities, the remaining as in Figure 5A.

likewise exhibit the same general trajectory with SYSTEMATICS the Sahabi specimen having a narrower mid-shaft. Langebaanweg Eurygnathohippus hooijeri is larger Order Perissodactyla Owen, 1848 than these specimens but has a similar overall Suborder Hippomorpha Wood, 1937 trajectory as the primitive Cormohipparion. Lotha- Superfamily Equoidea Hay, 1902 gam Sivalhippus turkanensis contrasts sharply in its Family Equidae Gray, 1821 heavier build with elevated midshaft (M3 and M4), Subfamily Equinae Steinmann & Döderlein, 1890 proximal articular (M5 and M6) and greater dis- Tribe Hipparionini Quinn, 1955 tal supraarticular (M10) diameter. Sahabi also has Genus Eurygnathohippus Van Hoepen, 1930 a partial distal MTIII, ISP6P34A that compares Type- Species: Eurygnathohippus feibeli Bernor & Harris, 2003 closely with Lothagam Stur and is referable to Etymology: Named in Honor of Professor Craig Feibel. cf. Sivalhippus turkanensis. Also, Samos Cremohippa- Age: Late Miocene of Africa, ca. 7-5.7 Ma. rion matthewi again shows extreme slender dimensions with greatly reduced midshaft (M3 and M4) Eurygnathohippus feibeli Bernor & Harris, 2003 proximal articular (M5 and M6) and distal articular (M10 and M11) dimensions. Figure 8B illustrates Synonymy: Hipparion turkanense Hooijer & Maglio, 1973: 311 that the partial Lothagam Eurygnathohippus feibeli is Hipparion turkanense Hooijer & Maglio, 1974: 8 similar to primitive Cormohipparion and Cremohippa- Not: Hipparion turkanense Hooijer, 1975: 19-22 Hipparion sp. cf. sitifense (Pomel, 1897) Tobien, 1982 rion mediterraneum. The Middle Awash preserves no “Hipparion” cf. sitifense Bernor et al., 1987 complete MTIIIs from the 6.0-5.6 Ma interval. Eurygnathohippus turkanense Leakey et al., 1996: 561 Sahabi Eurygnathohippus feibeli 571

Fig. 8 - MTIII log10 ratio Diagrams. A) Metatarsal III Sahabi, Europe- an and African Hipparions, log10 ratio, Ho Std. – abbreviations as in Figure 6A. B) Metatarsal III Lothagam, Europe- an, and African Hipparions, log10 ratio, Ho. Std. Locali- ties, as in Figure 6A.

Type Specimen: KNM-LT139, partial anterior foot. Description Type Locality: Lothagam Upper Nawata. Diagnosis PRGLÀHGIURP%HUQRU +DUULV LQGL- Dentition cates primitive characters for Old World hipparions; ** indicates au- There are 15 maxillary cheek teeth referred tapomorphies for Eurygnathohippus. to Eurygnathohippus feibeli in the Sahabi sample, all A medium sized hipparion with primitive facial morphology derived from the U1 unit (Table 2). including long preorbital bar and medially deep preorbital fossa*. Maxillary cheek teeth with elongate P2 anterostyle*; mesostyle is There are three txP2, ISP26P10A (left side; usually very narrow and blade like in early to middle wear becoming height = 32.0 mm), ISP75P17A (left side; height = rounded later in wear**; pre- and postfossettes are complexly pli- 27.3 mm) and ISP120P65A (left side; height = 24.3 FDWHGLQPLGGOHZHDU SURWRFRQHLVURXQGHGDQGOLQJXDOO\ÁDWWHQHG mm). ISP26P10A (Fig. 9A, labial and B, occlusal) in early wear becoming oval in middle wear and more rounded in late wear*; pli caballins are double to single*; hypoglyphs are moderately has the highest crown. The occlusal surface is com- deep to deep*. Mandibular cheek teeth with elongate metaconids in plete except for the mesio-lingual and distolingual early to middle wear becoming rounded in later wear**; metastylids portions and has: anterostyle elongate; mesostyle V- are square shaped in early to middle wear becoming rounded in late ZHDU OLQJXDÁH[LGVDUHVKDOORZDQGEURDGLQHDUO\ZHDUEHFRPLQJ shaped labially; pre- and postfossettes coming into GHHSHU9WR8VKDSHODWHULQZHDU SUHDQGSRVWÁH[LGVDUHFRPSOH[ wear and being moderately heavily plicated and sep- in early to middle wear becoming simple later in wear*; pli caballinids arated by a narrow groove; pli caballin is weakly bi- are single to absent*; ectostylids variably occur and sometimes rise ÀGSURWRFRQHRYDWHLQVKDSHDQGK\SRJO\SKPRG- high on the labial side of the crown*; protostylids are expressed in middle to late wear and when they occur they are open loops extend- erately deeply incised. ISP75P17A (Fig. 9C, labial ing far labially*. Postcrania are medium sized; metapodials are elon- and D, occlusal) is slightly more worn, with mesial- gate slender**; 1PHIIIs are elongate**. labial surface broken not preserving the anterostyle; 572 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

mesostyle is rounded and pre- and postfossettes are separated with moderately heavily complex plica- WLRQVDVLQ,633$SOLFDEDOOLQLVVWURQJO\ELÀG and protocone ovate; hypoglyph is as in ISP26P10A being moderately deeply incised. ISP120P65A is a left P2 that is the most worn P2 (Fig. 9E, labial and 9F, occlusal). The anterostyle is elongate; mesostyle is rounded, the pre- and postfossetes are complexly plicated, but this individual has the opposing bor- ders of pre- and postfossettes touching; pli caballin is multiple; protocone is ovate and hypoglyph is moderately deeply incised. There are three txP3, ISP4P16B (right side; height = 28.3 mm), ISP40P103A (left side; height = 23.2 mm) and ISP39P49A (left side; height unknown). ISP4P16B (Fig. 10A, labial and 10B, occlusal) has mesial border clearly leaning mesially with a fragmentary labial margin; occlusal surface has mesostyle narrowly rounded; pre- and postfossettes have complex margins; pli caballin is single; protocone is ovate and hypoglyph is moderately deeply incised. ISP40P103A (Fig. 10C, labial and 10D, occlusal) is in a late stage of wear and exhibits pre- Fig. 9 - Sahabi Eurygnathohippus feibeli P2; ISP26P10A: A) labial, B) and postfossettes well worn with reduction of plis occlusal; ISP75P17A: C) labial, D) occlusal; ISP120P65A: except the distal border of the prefossette which E) labial, F) occlusal. Scale bar 5 cm. remains complex; mesostyle is pointed; pli caballin is single, protocone is oval; hypoglyph is moderately deeply incised. 7KHUH DUH ÀYH W[3 ,633$ OHIW VLGH height = 43.2 mm), ISP1P85A (left side; height = 43.0 mm), ISP130P16A (left side; height = 41.5 mm), ISP35P99A (right side; height = 41.3 mm), ISP78P17A (left side; height unknown). ISP- 85P24A (Fig. 11A, labial and 11B, occlusal) is the highest crowned P4 (43.2 mm) in our sample and has a straight mesial wall and missing enamel on the mesial-buccal and mesial-lingual surfaces; mesostyle is very slender and blade like in buccal view (Fig. 11A). Occlusally, the mesostyle is very slender and pointed; pre- and postfossettes are coming into wear with only prefossette distal margin showing IDLQWSOLVSOLFDEDOOLQLVIDLQWO\ELÀGSURWRFRQHLV rounded labially with lingual margin broken; hypoglyph is deeply incised. This specimen is in an early stage-of-wear and suggests a maximum un- worn crown height of less than 50 mm. ISP1P85A (Fig. 11C, labial and 11D, occlusal) is slightly more worn than ISP85P24A with the occlusal surface ex- Fig. 10 - Sahabi Eurygnathohippus feibeli P3; ISP4P16B: A), labial, B) hibiting more clearly differentiated fossettes; pre- occlusal; ISP40P103A: C) labial, D) occlusal. Scale bar 5 cm. fossette is well preserved with complexity on the Sahabi Eurygnathohippus feibeli 573

Fig. 11 - Sahabi Eurygnathohippus feibeli P4; ISP85P24A: A) labial, B) occlusal; ISP1P85A: C) labial, D) occlusal; ISP- 130P16A: E) occlusal; ISP- 35P99A: F) labial, G) occlusal; ISP78P17A: H) occlusal. Scale bar 5 cm.

mesial margin and long, complex plications dis- There are 2 txM1, ISP52P103A (right side; tally; postfossette is in early wear with modest pli- height = 20.2 mm) and ISP76P108A (left side; height cations on the mesial margin and no plications yet unknown due to breakage of base). ISP52P103A appearing on the distal margin; pli caballin is long (Fig. 12A) is in late wear and in occlusal view has a and single; protocone is elongate-oval and distinct- rounded mesostyle; fossettes retain complex, albeit O\ ÁDWWHQHG OLQJXDOO\ K\SRJO\SK LV GHHSO\ LQFLVHG short plications; pli caballin is weakly double, proto- ISP130P16A is slightly more worn yet (Fig. 11E, FRQHLVRYDOVKDSHZLWKÁDWWHQHGOLQJXDOPDUJLQDQG occlusal view) and has lingual margin damaged; hypoglyph is deeply incised. ISP76P108A is a mid- mesostyle is again very pointed and blade-like; op- dle stage-of-wear specimen lacking the base and not posing margins of pre- and postfossettes are closely measurable for height; mesostyle is pointed labially opposed and touching each other; prefossette is and blade-like; fossettes are complexly plicated and heavily plicated on both mesial and distal margins; linked at their intersecting labial limit; pli caballin is pli caballin is not developed; protocone is missing; single, protocone ovate; hypoglyph deeply incised. hypoglyph is very deeply incised. ISP35P99A (Fig. There are three txM3, ISP16P108A (left side; 11F, labial and 11G, occlusal) has virtually the same height = 32.1 mm), ISP63P109A (right side; height crown height of ISP130P16A with better preserved = 22.2 mm) and ISP212P34A (left side; height = labial margin showing a blade-like mesostyle until 30.1 mm). ISP16P108A (Fig. 13A) does not have near the base of the tooth where it widens me- mesostyle preserved; prefossette has complex mar- sodistally; occlusally the mesostyle is pointed and slightly less blade-like than in previously described specimens; pre- and postfossettes are very closely opposed; prefossette is well preserved and complex; postfossette has only the mesial border preserved and moderately complex; pli caballin is single; protocone is ovate; hypoglyph is broken. ISP78P17A (Fig. 11H, occlusal view) is the most worn txP4 with all peripheral margins damaged; pre- and postfossette are complex preserving short, albeit complex plications; pli caballin is single; protocone is oval; Fig. 12 - Sahabi Eurygnathohippus feibeli M1; ISP25P103A: occlusal hypoglyph is deeply incised. view (labial view not available). Scale bar 5 cm. 574 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

Fig. 13 - Sahabi Eurygnathohippus feibeli M3, ISP16P108A: A) occlusal; ISP63P109A, B) occlusal; ISP212P34A: C) labial, D) occlusal. Scale bar 5 cm. gins, postfossette is less complex, and in particular the distal margin; pli caballin is single; protocone LV OLQJXDOO\ ÁDWWHQHG DQG ODELDOO\ URXQGHG K\SR- glyph is deeply incised. ISP63P109A (Fig. 13B) is in a late stage-of-wear but preserves blade-like mesostyle; complex prefossette, simpler postfossette; single pli caballin, ovate protocone, deeply incised hypoglyph. ISP212P34A (Fig. 13C and D) is leaning steeply distally (Fig. 13C); mesostyle is narrowly rounded labially; fossettes have complex opposing margins with a distinct accessory enamel ridge sepa- rating them; mesial border of prefossette and distal border of the postfossette are relatively simpler in their amplitude; pli caballin is simple; protocone is Fig. 14 - Sahabi Eurygnathohippus feibeli p4, ISP65P103A: A) labial, B) ovate and hypoglyph is deeply incised. occlusal; ISP84P24: C) labial, D) occlusal; ISP183P16A: E) There are 11 mandibular cheek teeth referred occlusal. Scale bar 5 cm. to Eurygnathohippus feibeli in the Sahabi sample, all derived from the U1 unit (Table 2). metaconid is rounded whereas metastylid is oblong; There are three tmp4, ISP65P103A (left side; WKHUHLVDVPDOOPHWDVW\OLGVSXUSUHDQGSRVWÁH[LG height = 44.8 mm), ISP84P24 (left side; height = KDYH VLPSOH PDUJLQV HFWRÁH[LG LV VKDOORZ ZLWK D 35.8 mm) and ISP183P16A (right side; height = YHU\VPDOOELÀGSOLFDEDOOLQLGDQGGLVWLQFWEXWVPDOO 40.8 mm). ISP65P103A (Fig. 14A and B) has a compressed ectostylid. ISP183P16A (Fig. 14E) has vertically straight mesial wall (Fig. 14A); in occlu- PHWDFRQLGDQGPHWDVW\OLGDVLQ,633SUHÁH[LG sal view metaconid is elongate, metastylid is round DQG SRVWÁH[LG DUH VOLJKWO\ SOLFDWHG HFWRÁH[LG KDV DQG OLQJXDÁH[LG LV VKDOORZ DQG EURDG SUHÁH[LG multiple pli caballinds and complex margin distally. DQG SRVWÁH[LG KDYH FRPSOH[ PDUJLQV HFWRÁH[LG There are seven tmm1s, ISP3P34B (right side; is shallow with a distinct pli caballinid; there is no height 55.8 mm; highest crowned cheek tooth in the protostylid nor ectostylid apparent. ISP84P24 (Fig. sample); ISP86P24 (right side; height = 40.6 mm); 14C and D) is straight walled mesially (Fig. 14D); ISP32P28 (left side; height = 39.6 mm), ISP71P103A Sahabi Eurygnathohippus feibeli 575

Fig. 15 - Sahabi Eurygnathohippus feibeli m1, ISP3P34B: A) labial, B) occlusal; ISP86P24: C) labial, D) occlusal; ISP32P28: E) labial, F) occlusal; ISP- 71P103A: G) labial, H) occlusal; ISP216P65A: I) labial, J) occlusal; ISP16P22A: K) labial, L) occlusal; ISP- 195P16A: M) labial, N) occlusal. Scale bar 5 cm.

(right side; height = 39.6 mm), ISP216P65A (right there is no pli caballinid but there is a tiny rounded side; 30.7 mm); ISP16P22A (left side; height = 27.0 ectostylid near the labial border. ISP216P65A (Fig. mm), ISP195P16A (right side; height = 16.6 mm). 15I and J) is poorly preserved; metaconid is round ISP3P34B (Fig. 15A and B) is very high crowned. and metastylid square with an oblique crack running Occlusally, metaconid is round, metastylid is square; WKURXJKLWSUHDQGSRVWÁH[LGVDUHVLPSOHOLQJXD- OLQJXDÁH[LGLVDVKDOORZ8VKDSHZLWKQRPHWDVW\O- ÁH[LGLVDGHHS9VKDSHWKHUHLVDQHORQJDWHRSHQ LG VSXU SUH DQG SRVÁH[LGV KDYH VLPSOH PDUJLQV SURWRVW\OLGH[WHQGLQJIDUODELDOO\HFWRÁH[LGLVYHU\ HFWRÁH[LGLVGHHSVHSDUDWLQJPHWDFRQLGDQGPHWD- elongate extending into the isthmus between metastylid; there is a distinct small ectostylid expressed conid and metastylid; there is no apparent pli cabal- both labially (Fig. 15A) and occlusally (Fig. 15B). linid or ectostylid. ISP16P22A (Fig. 15K and L) is as ISP86P24 (Fig. 15C and D) has metaconid elongate in ISP216P65A, remarkable again is the expression DQG PHWDVW\OLG URXQGHG OLQJXDÁH[LG LV D VKDOORZ of a buccally open protostylid extending far labially. 8VKDSH HFWRÁH[LG LV GHHS ZLWK D GLVWLQFW DOEHLW ISP195P16A (Fig. 15M and N) is in a very late wear small pli caballinid. ISP32P28 (Fig. 15E and F) has stage. The labial view (Fig. 15M) has a distinct ecto- URXQGHG PHWDFRQLG DQG PHWDVW\OLG OLQJXDÁH[LG LV VW\OLGFRQÀQHGWRWKHEDVHRI WKHFURZQRFFOXVDOO\ a deep V-shape with no metastyid spur; pre- and metaconid is rounded; metastylid is square; pre- and SRVWÁH[LGVKDYHVLPSOHPDUJLQVHFWRÁH[LGLVGHHS SRVWÁH[LGDUHVKDUSO\UHGXFHGLQVL]HZLWKVLPSOH lacking a pli caballinid; there is no ectostylid. ISP- PDUJLQVHFWRÁH[LGSHQHWUDWHVWKHLVWKPXVEHWZHHQ 71P103A (Fig. 15G and H) is not well preserved; metaconid and metastylid; there is no ectostylid, pli it preserves an elongate metaconid and squared caballinid or protostylid preserved. PHWDVW\OLGOLQJXDÁH[LGLVDGHHS9VKDSHSUHDQG There is single tmm2, ISP81P103A (right side; SRVWÁH[LGVKDYHVLPSOHPDUJLQVHFWRÁH[LGLVGHHS height = 43.6 mm; Fig. 16A and B). The metaconid 576 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

Q\D%HUQRUHWDO IXUWKHULGHQWLÀHGDFRP- plete MTIII of E. feibeli from Sahabi (67P16A) that was of appropriate length and proportions to be recognized as a member of this taxon. Table 2 lists an extensive suite of postcrania which we now refer to E. feibeli based on their comparable size, and in the case of MPIIIs their size and elongate-slender proportions. Figures 5A and 5B provide log10 ratio diagrams comparing Lothagam E. feibeli to a suite of European, West Asian and African 1PHIIIs. Sahabi E. feibeli (ISP32P25B) plots very close to the type Fig. 16 - Sahabi Eurygnathohippus feibeli m2, ISP81P103A: A) labial, B) Lothagam and Middle Awash (JAB-VP-1-1; 6.0 Ma; occlusal. Scale bar 5 cm. Bernor & Hailie Selassie 2009) E. feibeli as do Pik- ermi Cremohipparion mediterraneum and the primitive Old World Sinap (Turkey) Cormohipparion sinapensis. It is apparent that the 1PHIII proportions are shared primitively between Cormohipparion sinapensis, Cremo- hipparion mediterraneum and Eurygnathohippus feibeli. The type specimen of Lothagam MCIII exhibits a close length and proportion comparison with specimens from Sahabi (ISP82P17A), Pik- ermi (Crmed MEAN), Sinap (Csin_MEAN), and Middle Awash (AME-VP-1/175_Eufei and AMW- VP-1-15_Eufei) and Langebaanweg (Eu.hooijeri_ MEAN) (Figs. 7A and B). As with the 1PHIII, the MCIIIs of Lothagam and Sahabi Eurygnathohippus feibeliUHÁHFWSULPLWLYHHORQJDWHVOHQGHUSURSRUWLRQV Fig. 17 - Sahabi Eurygnathohippus feibeli m3, ISP77P17A: A) labial view, B) occlusal view. Scale bar 5 cm. shared with Eurygnathohippus hooijeri, Cormohipparion sinapensis and Cremohipparion mediterraneum. Sahabi MTIII Eurygnathohippus feibeli (ISP- is extremely elongate extending far mesially; meta- 3$ FRPSDUHVPRVWFORVHO\ZLWK%RX+DQLÀD VW\OLG LV URXQGHG OLQJXDÁH[LG LV VKDOORZ SUHÁH[LG (Algeria, 10.5 Ma) Cormohipparion africanum and Pik- LVSRRUO\GHÀQHGZKLOHSRVWÁH[LGLVLUUHJXODUVKDSH ermi Cremohipparion mediterraneum. Sinap Cormohippa- DQGFRPSOH[HFWRÁH[LGSOLFDEDOOLQLGDQGHFWRVW\OLG rion sinapensis has a similar length to E. feibeli but not are not observable; there is no protostylid. as narrow a midshaft width (M3). Langebaaneweg There is one tmm3, ISP77P17A (left side; Eurygnathohippus hooijeri is larger and does not have height = 43.5 mm; Fig. 17A and B). The labial view as exaggerated ratio between midshaft width (M3) shows that all cementum is lacking and that there is and midshaft depth (M4). It is apparent that Cormo- a strong protostylid on the mesio-labial border (Fig. hipparion sinapensis, “Cormohipparion” africanum, Cremo- 17A); occlusally metaconid and metastylid are round; hipparion mediterraneum exhibit similar trends to Eu- OLQJXDÁH[LGLVDGHHS8VKDSHSUHDQGSRVWÁH[LG rygnahohippus feibeli in length and slenderization of KDYHVLPSOHPDUJLQVHFWRÁH[LGLVGHHSSOLFDEDOOLQLG MTIII but were not as far advanced, while a larger and ectostylid are not present; protostylid does not horse, Langebaanweg Eurygnathohippus hooijeri like- ascend to occlusal level. wise shares similar log10 proportions. Our analyses Postcranial of 1PHIII, MCIII and MTIII show that Eurygnatho- %HUQRUHWDO LGHQWLÀHGD6DKDEL0&,,, hippus feibeli is derived from a primitive postcranial (82P17A, Fig. 3a) that is identical to the type speci- pattern likely stemming from the most primitive Old men of Eurygnathohippus feibeli from Lothagam, Ke- World hipparions related to Cormohipparion sinapensis. Sahabi Eurygnathohippus feibeli 577

DISCUSSION the labial side of the crown and rise only a fraction of the height of the crown terminating in a small ISP63P109A, an astragalus and an M3, and pointed-to-rounded structure. Other older hippa- ISP74P109A, a magnum are the only skeletal ele- rion assemblages from Sinap, Turkey (Bernor et al. ments that are derived from unit U2; the remain- 2003) and the Siwaliks, Pakistan (Bernor & Hussain ing 70 specimens are derived from unit U1. Sahabi’s 2005; Wolf et al. 2013), Chorora, Ethiopia (Bernor current correlation suggest that these fossils are HW DO DQG %RX +DQLÀD $OJHULD %HUQRU circa 6.8 Ma and approximately correlative with Eu- White 2009) have dentitions that are fully invested rygnathohippus feibeli’s type locality, Lothagam. Our in cementum so that if ectostylids occur on the base combined study of the postcrania (1PHIII, MC- of the crown, they are likely buried in cementum. III and MTIII) with the dental remains of Sahabi Our analyses of 1PHIII, MCIII and MTIII Eurygnathohippus feibeli suggests that this clade has a reveal that compared to the Hoewenegg Log10 deep time origin. standard, Sahabi, Lothagam and Middle Awash Bernor et al. (2017) reported a number of Eurygnathohippus feibeli exhibit elongate-slender pro- primitive dental characters in the Pannonian C hip- portions stemming from a plausible Cormohipparion parions from Atzelsdorf, Gaiselberg and Mariathal, sinapensis ancestry. For these three skeletal elements, Vienna Basin, Austria (11.4-11.0 Ma): relatively low elongate-slender proportions are similar between crown height (the greatest recorded crown height Cormohipparion sinapensis, Cormohipparion africanum, for Sahabi Eurygnathohippus feibeli being 55.8 mm for Cremohipparion mediterraneum, Eurygnathohippus feibeli ,633% RYDO SURWRFRQHV RIWHQ ZLWK ÁDWWHQHG and Eurygnathohippus hooijeri. The two Cormohipparion OLQJXDO ERUGHUV IUHTXHQW FRQÁXHQFH RI SUH DQG species, C. sinapensis and “C”. africanum are remark- postfossette plications, presence of pli caballinids ably similar in these postcranial proportions. Cre- and ectostylids on mandibular p2-m1. Our survey mohipparion mediterraneum, Eurygnathohippus feibeli and of Sahabi E. feibeli cheek teeth reveal: a relatively E. hooijeri exhibit similarities amongst themselves. low crown height (usually not greater than 50 mm), Cremohipparion mediterraneum and Eurygnathohippus fei- RYDO SURWRFRQHV ZLWK ÁDWWHQLQJ RFFXUULQJ ZLWK beli exhibit similarities in size and 1PHIII, MCIII VRPHLQFLGHQFHUDUHFRQÁXHQFHRI SUHDQGSRVW- and MTIII proportions, especially the relationships fossettes and associated presence of pli caballinids between narrow midshaft (M3) and deep midshaft and ectostylids in some mandibular cheek teeth. (M4) proportions of the metapodials. Bernor et al. Co-occurrence of pli caballinids associated with (2003) and Scott et al. (2003) noted this M3-M4 ectostylids are characteristic of Eurygnathohippus. proportion as the “Esme Acakoy Effect” and re- In fact, Eurygnathohippus species develop ectostylid lated it to increased cursoriality. Moreover, not to height, length and width progressively through the be overlooked the standing withers height of Eu- Plio-Pleistocene and are almost exclusively restrict- rygnathohippus feibeli has been estimated to have been ed in their occurrence to the African late Miocene – 110 cm. (Mauricio Anton, in Bernor & Harris 2003: Pleistocene, the last occurring there somewhat later Fig. 9.8), slightly shorter than the standing mount than 1 Ma. Eurygathohippus only occurs outside of of Hoewenegg Hippotherium primigenium (130-135 Africa in the Tatrot faunal zone of India, ca. 3.6-2.6 cm. Bernor et al. 1997: Figs. 5.2 and 5.3). Ma (Jukar et al. 2019). Eurygnathohippus feibeli is known to occur at The suite of primitive maxillary and mandib- Tizi N’Tadderht, Morocco, ca. 7 Ma (Cirilli et al. ular cheek tooth characters cited above were likely 2020) and Sahabi (Bernor et al. 2012). Eurygnatho- GLVWULEXWHG WKURXJK DOO ÀUVW RFFXUULQJ 2OG :RUOG hippus feibeli was originally recognized in the Lower hipparions. Woodburne (2009) and Bernor et al. and Upper Nawata members of the Nawata Forma- (2017) reported these characters for the Pannonian tion, Lothagam, Kenya with the Holotype, KNM- C hipparions, the oldest documented Old World LT139 occurring in the Upper Nawata. The Lower hipparions. Bernor et al. (2017) were able to observe Nawata member is dated 7.44 +/-0.05 Ma to 6.54 the crucial pli caballinid and ectostylid characters +/-0.04 Ma (McDougall & Feibel 2003). So, the because, for the most part, Pannonian C hipparions oldest Nawata assemblage is marginally older than lack cementum on their cheek tooth crown. Their Sahabi and Tizi N’Tadderht, while the type speci- Pannonian C hipparion ectostylids are “welded” to men from the Upper Nawata is arguably marginally 578 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

Fig. 18 - Biogeographic History of Eurygnathohippus. The genus arises from Old World Cormohipparion Datum of Sinap (Turkey) Cormohipparion sinapensis DQG%RX+DQLÀD $OJHULD “Cormohipparion” africanum. Eurygnathohippus feibeli earliest known occurrences from Lothagam (Ken- ya), Sahabi (Libya), and Tizi N’Tadderht (Morocco) with slightly younger recorded occurrence from JAB Middle Awash (Ethiopia); subsequent recorded succession in East and South Africa with Eurygnathohippus woldegabrieli from Aramis (Ethiopia), Eurygnathohippus cornelianus from Olduvai (Tanzania), and Eurygnathohippus hoojeri from Langenbaaweg (South Africa). younger (<6.54 Ma). The oldest sediments in the here, including E. cornelianus). Eurygnathohippus corne- Middle Awash are 6.0 Ma and a complete 1PHIII lianus ÀUVWRFFXUVDW2OGXYDL*RUJH FD0D DQG of E. feibeli occurs there at Jara-Borkana (JAB), 6.0 is remarkable for the expansion of premaxillary and Ma. (WoldeGabriel et al. 2009). Bernor & Hailie mandibular I1/i1 and I2/i2 with sharp reduction of Selassie (2009) have reported Eurygnathohippus aff. I3/i3. feibeli from younger Middle Awash levels dating 5.7- The origin, evolution and biogeography of 5.2 Ma. Mandibular cheek tooth pli caballinids and the Eurygnathohippus clade has only recently become ecstostylids persist through the Middle Awash suc- FODULÀHG 7KH ROGHVW 2OG :RUOG KLSSDULRQV KDYH cession, but postcranial log10 proportions do shift been reported from Pannonian C strata, Vienna later to larger size than E. feibeli in the section by Basin and are dated 11.4-11.0 Ma. Maxillary and 5.4-5.2 Ma. mandibular cheek teeth of these hipparions exhibit The next recognized Ethiopian Eurygnatho- a number of primitive characters discussed here, hippus species is E. woldegabrieli from the 4.4 Ma. with some of these being found in Eurygnathohippus. locality of Aramis (Bernor et al. 2013). There are Comparison of 1PHIII, MCIII and MTIII log10 distinct trends in the evolution of the African Eu- proportions exhibits evolutionary trends stemming rygnathohippus species E. feibeli – E. woldegabrieli – E. from Sinap, Turkey Cormohipparion sinapensis (10.8 hasumensis – E. cornelianus which include: increase in 0D DQG %RX +DQLÀD $OJHULD Cormohipparion afri- size through E. hasumensis; increase in crown height; canum (10.8 Ma) and evolving more slender, deep lengthening of MCIII and MTIII, increased height, keeled MCIII and MTIII in Cremohipparion mediter- length and width of ectostylids (Bernor et al. 2005; raneum and Eurygnathohippus feibeli. In that Cremohip- Sahabi Eurygnathohippus feibeli 579

parion mediterraneum consistently lacks pli caballinids RI )ORUHQFHIRUÀQDQFLDOVXSSRUW7KLVFRQWULEXWLRQLVIUDPHGZLWKLQ and ectostylids, it is derived compared to Eurygna- a wider project on late Neogene vertebrate evolution at the University of Florence (coordinator LR); background work for this paper has thohippus feibeli and its descendants. The genus Eu- been supported by the University of Florence (Fondi di Ateneo), and rygnathohippus is therefore validated now based on NGS (8788-10) to LR. This is FuTRES project publication number 11. both dental and postcranial characters. Figure 18 il- Author contributions. R.L.B. and O.C. conceived the study and wrote the manuscript with contribution of N.B. and L.R.; R.L.B. and lustrates the Late Miocene - Pliocene biogeographic O.C. performed the analyses; all authors discussed the results, com- record of Eurygnathohippus. PHQWHGRQWKHPDQXVFULSWDQGDSSURYHGWKHÀQDOPDQXVFULSW

REFERENCES CONCLUSIONS

Eurygnathohippus is a distinct clade of hippa- Armour-Chelu M. & Bernor R.L. (2011) - Equidae. In: Harrison T. (Ed.) - Paleontology and Geology of Laetoli: Human rionine horses, with Eurygnathohippus feibeli having a evolution in context (Fossil hominins and the associated known geographic range from Kenya, to Ethiopia, fauna, Vol. 2): 295-326. Springer, Dordrecht. Libya and Morocco, and a chronologic range of Bernor R.L. (1985) - Systematic and evolutionary relationships of the hipparionine horses from Maragheh, Iran (Late approximately 7.0 – 5.7 Ma. Eurygnathohippus feibeli Miocene, Turolian age). Paleovertebrata, 15: 173-269. had primitive cheek tooth characters including oc- Bernor R.L. & Armour-Chelu M. (1999) - Towards an currence of co-occurring ectostylids and pli cabal- evolutionary history of African hipparionine horses. In: linids on the mandibular cheek teeth; very narrow Bromage T. & Schrenk F. (Eds) - African Biogeography, Climate Change and Early Hominid Evolution: 189-215. (knife-like) mesostyles with complex plications of Oxford University Press, New York. the pre- and postfossettes in middle wear in the max- Bernor R.L. & Haile-Selassie Y. (2009) - Equidae. In: Haile- illary cheek teeth; and a maximum crown height of Selassie Y. & WoldeGabriel G. (Eds) - Ardipithecus kadabba: 56 mm. Eurygnathohippus’ cheek tooth morphology Late Miocene Evidence from the Middle Awash, Ethiopia: 397-428. University of California Press, Berkeley. is clearly derived from earliest occurring hipparions Bernor R.L. & Harris J.M. (2003) - Systematics and evolutionary from the Pannonian C, Austria (Bernor et al. 2017) biology of the Late Miocene and Early Pliocene and its postcranial anatomy would appear to be de- hipparionine horses from Lothagam, Kenya. In: Harris J.M. & Leakey M.G. (Eds) - Lothagam: The Dawn ULYHGIURPÀUVWRFFXUULQJ2OG:RUOGCormohipparion of Humanity in Eastern Africa: 387-438. Columbia sinapensis from Sinap, Turkey (Bernor et al. 2003) and University Press, New York. “Cormohipparion” africanum %RX+DQLÀD$OJHULD %HU- Bernor R.L. & Hussain S.T. (1985) - An Assessment of nor & White 2009). Moreover, the slender 1PHIIIs, the Systematic, Phylogenetic and Biogeographic Relationships of Siwalik Hipparionine Horses. Journla of MCIIIs and MTIIIs compare closely with Pikermi Vertebrate Paleontology, 5: 32-87. Cremohipparion mediterraneum and are divergent from Bernor R.L. & Kaiser T.M. (2006) - Systematics and Paleoecology primitive Hippotherium primigenium. The Eurygnathohip- of the Earliest Pliocene Equid, Eurygnathohippus hooijeri n. pus clades’ evolutionary radiation is restricted to Af- sp. from Langebaanweg, South Africa. Mitteilungen aus dem Hamburischen Zoologischen Museum und Institut, 103: 147-183. rica until the Pliocene when it extended its range into Bernor R.L. & Rook L. (2008) - A Current View of As Sahabi India during the Late Pliocene, ca. 3.6-2.6 Ma (Jukar Large Mammal Biogeographic Relationships. Garyounis et al. 2019). Whereas Zouhri and Bensalmia (2005) 6FLHQWLÀF%XOOHWLQ, Special Issue 5: 283-290. Bernor R.L. & Scott R.S. (2003) - New interpretations of have recognized Eurygnathohippus at the subgeneric the systematics, biogeography and paleoecology of the rank (Proboscidipparion (Eurygnathohippus)), we follow Sahabi hipparions (latest Miocene), Libya. Geodiversitas, other authors recognizing Eurygnathohippus as a dis- 25: 297-319. tinct clade of generic rank (Bernor & Harris 2003; Bernor R.L. & Sen S. (2017) - The early Pliocene Plesiohipparion and Probiscidipparion (Equidae, Hipparionini) from Çalta, Bernor & Hailie Selassie 2009; Bernor et al. 2010; Turkey (Ruscinian Age, c. 4.0 Ma). Geodiversitas, 39: 28-41. Bernor et al. 2012; Cirilli et al. 2020). Bernor R.L. & Sun B.Y. (2015) - Morphology through ontogeny of Chinese Proboscidipparion and Plesiohipparion Acknowlegements: NB and MHS wish to acknowledge Libyan and observations on their Eurasian and African relatives. Co-Directors of the East Libya Neogene Research Project, Ahmed Vertebrata PalAsiatica, 53: 73-92. Muftah, and the Department of Earth Sciences, University of Beng- Bernor R.L. & Tobien H. (1989) - Two small species of hazi, Libya. RLB wishes to acknowledge research funding by NSF Cremohipparion (Mammalia, Equidae) from Samos, Greece. EAR grants 8806645, 0125009, 1113175, 1558586; DBI grant 1759882 Mitteilungen Bayerischen Staatssammlung für Palaeontologie und for the FuTRES database; BCS0321893 (to F.C. Howell and T.D. historische Geologie, 29: 207-226. White) which provided data and background investigations critical to Bernor R.L. & White T.D. (2009) - Systematics and Biogeography this manuscript. OC acknowledges University of Pisa and University of “Cormohipparion” africanum, Early Vallesian (MN 9, ca. 580 Bernor R-L., Boaz N.T., Cirilli O., El-Shawaihdi M.H. & Rook L.

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