Articles

Print Email

An exceptionally well-preserved skeleton of Thomashuxleya externa (Mammalia, Notoungulata), from the Eocene of Patagonia, Argentina

Juan D. Carrillo and Robert J. Asher

Plain Language Abstract

Notoungulata is an enigmatic group of placental mammals that inhabited South America during most of the past 60 million years. Despite more than a century of study, the relationships of nototoungulates to other mammals are not fully resolved and remain a major challenge in paleomammalogy. Here, we describe one of the oldest and most complete skeletons of a notoungulate from the middle Eocene of Patagonia, Argentina, which lived about 45 million years ago. The association of a skull with teeth and other skeletal remains allows us to identify the specimen as Thomashuxleya externa (Isotemnidae), estimate its body mass, describe its bone microanatomy, and examine its relationships to other mammals. This animal likely weighed about 84 ± 24.2 kg. Analysis of microstructure of bones in cross section shows that the new specimen was skeletally mature. In order to infer the position of Thomashuxleya in the evolutionary tree of mammals, we combined sequences from DNA and collagen sequences (known for living and some very recent fossils), and morphological data. This analysis favors a limited number of possible phylogenetic relationships, with possible affinities to even- and odd-toed ungulates, endemic African mammals, or other endemic South American mammals.

Resumen en Español

Un esqueleto excepcionalmente bien preservado de Thomashuxleya externa (Mammalia, Notoungulata), del Eoceno de Patagonia, Argentina

Describimos uno de los esqueletos de notoungulados más antiguos con elementos cráneo-dentales y postcraneales asociados: Thomashuxleya externa (Isotemnidae) de Cañadón Vaca en Patagonia, Argentina (subedad Vaquense de la Edad Mamífero Casamayorense, Eoceno medio). Proveemos estimaciones de masa corporal dadas por distintos elementos del esqueleto, describimos la histología de los huesos, y estudiamos la posición filogenética. Notamos diferencias en las escápulas, húmeros, ulnas y radios del nuevo espécimen en comparación con otros especímenes previamente referidos a este taxon. Estimamos una masa corporal de 84 ± 24,2 kg, mostrando que los notoungulados habían adquirido una gran masa corporal ya en el Eoceno medio. La histología de huesos muestra que el nuevo espécimen era esqueletalmente maduro. El nuevo material soporta la posición de Thomashuxleya como un miembro temprano y divergente de Toxodontia. Dentro de los placentarios, nuestro análisis filogenético de una matriz combinada de ADN, colágeno y morfología favorece únicamente un número limitado de posibles relaciones filogenéticas, pero no puede aún arbitrar entre afinidades potenciales con Afrotheria or Laurasiatheria. Sin restricciones, la parsimonia máxima soporta Thomashuxleya y Carodnia con Afrotheria. Con Notoungulata y Litopterna restringidos como monofiléticos (incluyendo Macrauchenia y Toxodon conocidos por colágenos), estos clados son reconstruidos en el stem de Euungulata (i.e., Perissodactyla y Artiodactyla). El análisis bayesiano no restringido soporta débilmente la posibilidad de que Thomashuxleya sea stem Xenarthra; con Notoungulata y Litopterna restringidos como monofiléticos, los dos clados son recuperados como grupo hermano de Perissodactyla. Datos anatómicos muestreados hasta el momento para Thomashuxleya, combinados con aminoácidos de colágeno para meridiungulados pleistocenos, limitan substancialmente el número de afinidades posibles para las especies endémicas de América del Sur dentro de los mamíferos, aunque aún existe ambigüidad.

Palabras clave: América del Sur; Toxodontia; Litopterna; masa corporal; filogenia

Traducción: Diana Elizabeth Fernández

Résumé en Français

text

Translator: Antoine Souron

Deutsche Zusammenfassung

Ein außerordentlich gut erhaltenes Thomashuxleya externa Skelett (Mammalia, Notoungulata), aus dem Eozän von Patagonien, Argentinien

Wir beschreiben eines der ältesten Notoungulaten-Skelette mit assoziierten craniodentalen und postcranialen Elementen: Thomashuxleya externa (Isotemnidae) aus Cañadón Vaca in Patagonien, Argentinien (Vacanium Unterstufe der Casamayorium SALMA, mittleres Eozän). Wir schätzen das Gewicht mit Hilfe verschiedener Skelett-Elemente, beschreiben die Knochenhistologie und untersuchen die phylogenetische Position. Wir erfassen Unterschiede bei den Scapulae, Humerii, Ulnae und Radii des neuen Stückes im Vergleich mit anderen Stücken, die vorher diesem Taxon zugeschrieben wurden. Wir errechnen ein Gewicht von 84 ± 24.2 kg, und zeigen damit, dass Notoungulaten im mittleren Eozän ein hohes Gewicht erreicht hatten. Die Knochenhistologie zeigt, dass das neue Stück ein ausgewachsenes Skelett hatte. Das neue Material unterstützt die Platzierung von Thomashuxleya als ein frühes, divergentes Mitglied der Toxodontia. Unter den Plazentatieren favorisiert unsere phylogenetische Analyse mit kombinierter DNA, Kollagen und morphologischer Matrix nur eine limitierte Anzahl an phylogenetischen Verwandtschaftsbeziehungen, jedoch kann nicht genau entschieden werden zwischen einer möglichen Zugehörigkeit zu den Afrotheria oder Laurasiatheria. Ohne Constraint unterstützt Maximale Parsimonie Thomashuxleya und Carodnia mit den Afrotheria. Wenn Notoungulata und Litopterna als monophyletisch (mit Macrauchenia und Toxodon bekannt für Kollagene) constraint sind, werden diese Kladen am Stamm zu den Euungulata (i.e., Perissodactyla und Artiodactyla) rekonstruiert. Nicht-constraint unterstützt die Bayesianische Analyse schwach die Möglichkeit dass Thomashuxleya ein Stamm- Xenarthra ist; wenn Notoungulata und Litopterna als monophyletisch constraint sind, werden die zwei Kladen als Schwestertaxa zu den Perissodactyla installiert. Anatomische Daten, die bisher von Thomashuxleya gesammelt und mit Kollagen-Aminosäuren kombiniert wurden, limitieren die Anzahl möglicher Zugehörigkeiten für endemische südamerikanische Arten unter den Säugetieren erheblich, allerdings verbleiben immer noch Unklarheiten.

Schlüsselwörter: Südamerika; Toxodontia; Litopterna; Körpergewicht; Phylogenie

Translator: Eva Gebauer

Arabic

Translator: Ashraf M.T. Elewa

 

 

FIGURE 1. Geographical and stratigraphical occurrence of MPEF-PV 8166. 1 location of Cañadón Vaca, Chubut, Argentina; 2 Paleogene time table and South American Land Mammal Ages (SALMAs) after (Woodburne et al. 2014a,b); 3 skeletal restoration of Thomashuxleya modified from Simpson (1936); 4 artistic reconstruction of Thomashuxleya externa (by Stjepan Lukac).

 figure1

FIGURE 2. Skull of T. externa (MPEF-PV 8166). 1 ventral view; 2 lateral view; 3 occiput in caudal view; 4 detail of upper dentition in occlusal view. Abbreviations are prot=protocone (part of the protoloph), par=paracone (part of the ectoloph), parst=parastyle, met=metacone (part of the ectoloph), metst=metastyle, meph=metaloph, pr.l.f.=primary lingual fold, m.cin=mesial cingulum, l.cin=lingual cingulum.

figure2 

FIGURE 3. Mandible of T. externa (MPEF-PV 8166) in 1 dorsal and 2 lateral views; 3 lower dentition in occlusal view. Abbreviations are tri=trigonid, tal=talonid, prod=protoconid, metd=metaconid, entd=entoconid, hypd=hypoconulid.

 figure3

FIGURE 4. Scapulae and humeri of T. externa (MPEF-PV 8166). 1 right and 2 left scapulae in proximal view; 3 left scapula in dorsolateral view; right and left humeri in 4 right and left humeri in anterior (top) and distal (bottom) views; 5 right and left humeri in posterior view.

 figure4

FIGURE 5. Forelimb of T. externa (MPEF-PV 8166). 1 right and left ulnae in frontal view; 2 left ulna in medial view; right radius in 3 frontal, 4 lateral, and 5 posterior views.

 figure5

FIGURE 6. Hindlimb of T. externa (MPEF-PV 8166). right pelvis in 1 dorsal and 2 lateral views; 3 right femur in anterior view; 4 right tibia in proximal (top), anterior (middle) and distal (bottom) views; left astragalus in 5 dorsal and 6 plantar views; 7 right navicular in proximal view; 8 navicular and entocuneiform in plantar views.

figure6 

FIGURE 7. Bone histology and microstructure of T. externa (MPEF-PV 8166). 1 Cross section of the midshaft of the right femur; 2 same as 1 after conversion to a binary image (black represents bone and white the cavities); 3 bone histology under linear polarized light, with black arrows pointing the lines of arrested growth (LAGs). OCL= Outer circumferential layer. 4 Bone histology under cross polarized light.

figure7 

FIGURE 8. Strict consensus of 281 trees, 420 steps in length showing the phylogenetic relationships of Thomashuxleya within Notoungulata based on the morphological dataset of Deraco and García-López (2015). Numbers indicate bootstrap values above 50.

figure8a 

 

FIGURE 9. Strict consensus of 510 trees, 122374 steps in length from unconstrained parsimony analysis of combined proteomic and morphological data.

figure9 

FIGURE 10. Strict consensus of 620 trees, 122391 steps in length from parsimony analysis of combined proteomic and morphological data constraining monophyly of each of two clades (but not both together): Notoungulata (i.e., Thomashuxleya and Toxodon) and Litopterna (i.e., Protolipterna and Macrauchenia).

 figure10

FIGURE 11. Optimal Bayesian tree (i.e., 50% majority rule of post-burn-in trees) of combined proteomic and morphological data. Numbers represent Bayesian posterior probabilities; daggers indicate fossil taxa.

figure11 

FIGURE 12. Optimal Bayesian tree (i.e., 50% majority rule of post-burn-in trees) of combined proteomic and morphological analysis constraining monophyly of each of two clades (but not both together): Notoungulata (i.e., Thomashuxleya and Toxodon) and Litopterna (i.e., Protolipterna and Macrauchenia). Numbers represent Bayesian posterior probabilities; daggers indicate fossil taxa.

figure12

 

TABLE 1. Best partition scheme for Bayesian analysis as obtained from Partition Finder (Lanfear et al., 2012).

Best model Subset partitions Subset sites
JTT+G TTN 1-1479
JTT+G CNR1 1480-1814
JTT+G BCHE 1815-2146
JTT+G EDG1 2147-2466
JTT+G RAG1 2467-3066
JTT+G RAG2 3067-3215
JTT+G ATP7A 3216-3444
JTT+G TYR1 3445-3587
JTT+G Adora3 3588-3698
JTT+G BDNF 3699-3885
JTT+G ADRB2 3886-4153
JTT+G PNOC 4154-4260
JTT+G A2AB 4261-4543
JTT+G BRCA1, BRCA2 4544-5574, 5575-7256
JTT+G APOB, DMP1 7257-7710, 9718-10592
JTT+G GHR 7711-8026
JTT+G VWF 8027-8417
JTT+G ENAM 8418-9717
JTT+G IRBP 10593-11010
MTMAM+G Collagen alpha 1 and 2 11011-13038
Standard discrete Morphology 13039-16698

 

TABLE 2. Skeletal elements of isotemnid specimens from Cañadón Vaca.

  T. externa
MPEF-PV 8166
T. externa
MNHN CAS 844
T. externa
MNHN CAS 64
T. externa
AMNH 28698
T. externa
AMNH 28447
T. externa
AMNH 28905
T. externa
AMNH 28563
cf. T. externa
AMNH 142463
A. distentus
AMNH 28906
A.distentus
AMNH 28647
P. similis
AMNH 28904
P. similis
AMNH 28635
Isotemnidae indet.
AMNH 28690
Skull x x   x             M1 only    
Mandible x   x   x                
Scapula x         x     x        
Humerus x         x x   x   x    
Ulna x         x x   x   x    
Radius x           x   x x x    
Manus                 x x x    
Pelvis x         x              
Femur x         x           x x
Tibia x                   x x x
Pes x             x x   x   x

 

TABLE 3. Dental measurements of Thomashuxleya; * =taken from Simpson (1967).

    p1 p2 p3 p4 m1 m2 m3
    Length Width Length Width Length Width Length Width Length Width Length Width Length Width
T. rostrata MACN 10370* 13.7 11.8 17.5 12.7 18.1 14.8 20.9 16.6            
MACN 10539*             19.9 17.8 26 19.8 26.4 19.5 37.2 16.9
MACN 10546*             21.5 16.8            
AMNH 28692*         19.5 16.5     26 16.4 28.5 18.8    
AMNH 28764*             21.8 13.7            
                             
Mean 13.7 11.8 17.5 12.7 18.8 15.7 21.0 16.2 26 18.1 27.5 19.2 37.2 16.9
SD NA NA NA NA 1.0 1.2 0.8 1.8 0.0 2.4 1.5 0.5 NA NA
n 1 1 1 1 2 2 4 4 2 2 2 2 1 1
T. externa MACN 10540*         16.5 14.6 19 17.2 21   28   37  
MACN 10537*             16.3 13 19.5 14 23 15.5    
AMNH 28447*     14.2 11.1 16.2 11.6 18.1 13 22.0 15.6 27.5 16.5 31.6 15.8
AMNH 28697*             17.3 14.2 23.2 15.9 25.5 17.2 36 16.6
AMNH 28756*     14.7 10.9 15.7 12.8 16.4 14.2 21.8 16.3 25.6 17.8 32.3 16.3
AMNH 28698* 11.0 10.0 15.1 12.6 16.7 13.6 16.5 14.6 24 16.1 26 17.8 37 17
AMNH 28686*                         34.5 17.0
AMNH 28822*                 20 16.4 23 18.0    
Mean* 11 10 14.7 11.5 16.3 13.2 17.3 14.4 21.6 15.7 25.5 17.1 34.7 16.5
SD* NA NA 0.5 0.9 0.4 1.3 1.1 1.5 1.6 0.9 2.0 1.0 2.4 0.5
n* 1 1 3 3 4 4 6 6 7 6 7 7 6 5
MPEF-PV 8166 12.8 8.3 15.4 10 16.5 10.1 16.4 13.3 20.1 15.6 22.5 15.3 32.3 15.7
 
 

 

P1 P2 P3 P4 M1 M2 M3

 

 

Length Width Length Width Length Width Length Width Length Width Length Width Length Width
T. rostrata MACN 10370* 15.4 15.7 17.0 27.2 19.5 31.2 21 35            
MACN 10542*                 29.5 41.8 33.0 44.2 28.8 40.8
Mean* 15.4 15.7 17 27.2 19.5 31.2 21 35 29.5 41.8 33 44.2 28.8 40.8
SD* NA NA NA NA NA NA NA NA NA NA NA NA NA NA
n* 1 1 1 1 1 1 1 1 1 1 1 1 1 1
T. externa MACN 10543*                 24 34 28.5 35.9    
AMNH 28699*     17.5 22.1 16.8 26.4 18.5 32.1 23.8 35.8 26.7 42   39.5
AMNH 28757* 13.8 11.5 15.2 22.1 18 26     25.7   27.2 39.2    
AMNH 28698* 10 11     16   18 33.2 23.9 38.7 27.2 41 26 41
MNHN CAS 844 10.84 13.86 17.79 22.93 18.94 26.80 19.13 31.25 21.40 32.75 22.71 35.98 26.55 35.46
Mean* 11.5 12.1 16.8 22.4 17.4 26.4 18.5 32.2 23.8 35.3 26.5 38.8 26.3 38.7
SD* 2.0 1.5 1.4 0.5 1.3 0.4 0.6 1.0 1.5 2.6 2.2 2.8 0.4 2.9
n* 3 3 3 3 4 3 3 3 5 4 5 5 2 3
MPEF-PV 8166 10.2 10.5 14.0 16.2 15.0 21.6 14.6 25.9 25.2 31.3 27.9 36.9 24.0 32.0

 

 

TABLE 4. Postcranial measurements of MPEF-PV 8166. * Translated from Spanish in Elissamburu (2012).

  Value
(mm)
  Acronym
  Left Rigth   Scott
(1990)
Elissamburu
(2012)
Scapula  
Height of the spine 31.0 31.4      
Humerus  
Humerus functional length* 193 204   H1 LFH
Humerus trochlear diameter* 52.0 43.3   H4 DtrH
Maximum length 211 210      
Maximum diameter of the head 44.0 40.5      
Maximum diameter of the mayor tuberosity   46.6      
Maximum diameter of the minor tuberosity   16.6      
Maximum widht of the trochlea 30        
Radius  
Maximum length 155 153      
Maximum mediolateral width of the medial shaft 14.1 14.0      
Maximum diameter of the head 32.0        
Minimum diameter of the head 20.3 20.4      
Maximum diameter of the neck 20.3 19.5      
Mediolateral width of the distal epiphysis   36.0      
Diameter perpendicular to the maximum width of the distal epiphysis   31.6      
Ulna  
Anteroposterior diameter of the diaphysis 28.3 28.1      
Olecraneum height 64.9 63.7      
Anteroposterior diameter of the oleocranon 32.6        
Proximo-distal length of the trochlear notch 35.9        
Trochlear notch width   32.6      
Width of anconeal process   20.5      
Femur  
Anteroposterior diameter of the shaft   25.5   F7 DAPF
Mediolateral diameter of the shaft   36.2   F6 DTF
Tibia  
Mediolateral diameter of proximal epiphysis   55.0   T2 DTpT
Anteroposterior diameter of proximal epiphysis   44.8      
Lateral condyle transverse width   28.0      
Lateral condyle anteroposterior width   25.0      
Astragalus  
Transverse width of tibial trochlea 27.7     Li 1  
Minimum width of the neck 14.8        
Width sustentacular facet 17.4        
Navicular  
"Dorsal-plantar" width   25.6      
Astragalar facet transverse width   24.0      
Astragalar facet dorsoventral depth   25.0      
Pelvis  
Maximum width of the ilium, above the acetabulum   42.3      

 

TABLE 5. Isotemnid astragali measurements in mm.

Specimen No. Locality Maximum length Trochlear width Maximum width Head width
MPEF-PV 8166 Cañadón Vaca   27.7    
AMNH 142463 Cañadón Vaca   35.9 41.4  
AMNH FM 14501 "Notostylops beds" 32.8 21.8 32.1 17.7
AMNH 28690 Cañadón Vaca 22 12 20.6  
AMNH 142464 Cañadón Vaca 20.5 8.9 16.7 9.3

 

TABLE 6. Results from the Wilcoxon signed ranks test comparing topologies carried out in PAUP. Meridungulata = constraint with all SANUs within a clade; N/L= Notoungulata (Thomashuxleya, Toxodon) and Litopterna (Macrauchenia, Protolipterna) monophyly constraints for each clade (but not both together); p values greater than 0.05 indicate no difference between optimal and competing topology.

Topology Tree length Rank sums N z p
  122374 (best)      
N/L 122391 52385.0/--48640.0 449 -0.77 0.4390
Meridungulata 122424 214600.5/-193555.5 903 -1.49 0.14
 

APPENDIX 1.

Definitions, measurements (in mm, unless otherwise stated) and equations used (Janis, 1990; Scott, 1990; Tsubamoto, 2014) to estimated the body mass (BM) in kg of MPEF-PV 8166. PE= Percent of error.

Variable Acronym Definition Type Dataset Value Equation R2 % PE Slope Intercept BM BM + PE BM - PE
Lower molar row length LMRL Measured along the base of the teeth Dental All ungulates 75.6 log BM= 3.265*log(LMRL)-0.536 0.941 31.9 3.27 -0.536 396 522 269
First lower molar length FLML Measured at the occlusal surface of the tooth Dental All ungulates 20.1 log BM= 3.263*log(FLML)+1.337 0.93 34.6 3.26 1.34 389 524 254
First lower molar width FLMW   Dental All ungulates 15.6 log BM= 2.909*log(FLMW)+2.030 0.92 38.4 2.91 2.030 316 437 194
First lower molar area FLMA FLMA= FLML*FLMW Dental All ungulates 313.3 log BM= 1.553*log(FLMA)+1.701 0.93 33.2 1.55 1.7 378 503 252
Second lower molar length SLML Measured at the occlusal surface of the tooth Dental All ungulates 22.5 log BM= 3.201*log(SLML)+1.130 0.94 31.9 3.2 1.130 289 381 197
Second lower molar area SLMA SLMA= SLML*Second Lower Molar Width Dental All ungulates 343.7 log BM= 1.563*log(SLMA)+1.541 0.94 33.5 1.56 1.54 320 427 213
Third lower molar area TLMA TLMA= Third lower molar length *Third lower molar width Dental All ungulates 508.9 log BM= 1.580*log(TLMA)+1.404 0.93 33.1 1.580 1.4 479 638 321
Second upper molar length SUML Measured at the occlusal surface of the tooth Dental All ungulates 27.9 log BM= 3.184*log(SUML)+1.091 0.93 34.7 3.18 1.09 494 666 323
Second upper molar width SUMW Measured at the occlusal surface of the tooth Dental All ungulates 36.9 log BM= 3.004*log(SUMW)+1.469 0.92 38.9 3 1.47 1501 2085 917
Second upper molar area SUMA SUMA=SUML*SUMW Dental All ungulates 1029.5 log BM=1.568*log(SUMA)+1.277 0.94 32.7 1.57 1.28 1002 1329 674
Posterior jaw length PJL Measured as the horizontal distance from the back of the jaw condyle to the posterior border of m3 Crania All ungulates 65.3 log BM= 2.412*log(PJL)+0.031 0.93 36.5 2.41 0.03 26 35 16
Maximum width of the mandibular angle WMA Measured from the junction of the posterior part of m3 with the jaw to the maximally distant point on the angle of the jaw Crania All ungulates 105.5 log BM= 2.803*log(WMA)-0.352 0.92 40.5 2.8 -0.35 209 293 124
Length of the ridge for the masseteric attachment MFL Measured from the posterior portion of the jaw glenoid to the most anterior extent of the scar for the origin of the masseter muscle Crania All ungulates 153 log BM= 2.950*log(MFL)-1.289 0.94 35.0 2.950 -1.289 143 193 93
Humerus functional length (cm) H1 The distance between the most proximal point of the head and the most distal point of the trochlea Postcranial All ungulates 19.85 log BM= 3.4026*log(H1)-2.3707 0.92 28 3.4026 -2.37 111 142 80
Humerus trochlear diameter (cm) H4 The transverse distance of the distal articular surface Postcranial All ungulates 4.76 log BM= 2.4815*log(H4)+0.4516 0.95 22 2.4815 0.45 136 166 106
Anteroposterior diameter of the femur (cm) F6 The transverse diameter of the diaphysis at its midpoint Postcranial All ungulates 3.62 log BM=2.8210*log(F6)+0.9062 0.94 23 2.8210 0.91 304 373 234
Mediolateral diameter of the shaft (cm) F7 The anteroposterior diameter of the diaphysis at its midpoint Postcranial All ungulates 2.55 log BM=2.6016*log (F7)+0.9119 0.94 26 2.6016 0.91 93 117 69
Diametro transverso proximal de la tibia (cm) T2 The transverse diameter of the tibia’s proximal epiphysis Postcranial All ungulates 5.5 log BM=2.8491*log(T2)-0.2495 0.95 21 2.8491 -0.25 72 88 57
Transverse width of tibial trochlea Li1   Astragalus Various mammals 27.7 ln BM= 2.789*ln(Li1)+2.078 0.98 28.83 2.79 2.08 84 109 60

 

 

APPENDIX 2.

Selected measurement (in cm) and multivariate equations used (Mendoza et al., 2006) to estimated the body mass in kg (BM) of MPEF-PV 8166. PE= Percent of error.

Adj. R2 %MPE mid
PE
LMRL LPRL JMA JMC JD JMB BM BM+ mid PE BM -mid PE
0.98 21-25 23 7.56 5.86 6.53 10.55 4.88   177 217 167
0.98 21-25 23 7.56 5.86 6.53 10.55 4.88 11.6 184 226 174
 

author1Juan D. Carrillo. Paläontologisches Institut und Museum, Universität Zürich. Karl-Schmid-Strasse 4, 8006 Zürich, Switzerland and Department of Zoology, University of Cambridge. Downing Street CB2 3EJ, Cambridge, UK. This email address is being protected from spambots. You need JavaScript enabled to view it.

Juan Carrillo is a PhD student at the Paleontological Institute and Museum of the University of Zurich, Switzerland and SNF fellow at the Museum of Zoology in Cambridge, UK. His research includes the systematics and paleobiology of south american mammals (native ungulates and rodents)

divider

author2Robert J. Asher. Department of Zoology, University of Cambridge. Downing Street CB2 3EJ, Cambridge, UK. This email address is being protected from spambots. You need JavaScript enabled to view it.

Robert Asher is Senior Lecturer and Curator of Vertebrates at the Museum of Zoology in Cambridge, UK. His research interests include development and constraint among southern placental mammals (Afrotheria and Xenarthra), the evolution of endemic African mammals, and the diversification of therian mammals.