Megatherioidea

Casali, Daniel M, Boscaini, Alberto, Gaudin, Timothy J & Perini, Fernando A, 2022, Reassessing the phylogeny and divergence times of sloths (Mammalia: Pilosa: Folivora), exploring alternative morphological partitioning and dating models, Zoological Journal of the Linnean Society 196 (4), pp. 1505-1551 : 1525

Megatherioidea

PP = 99, age = 26.32 Mya (21.32–30.99).

The clade, composed of Pelecyodon , Schismotherium , Megalonychidae and Megatheriidae , was recovered in all analyses using MP methods and all Bayesian analyses using H models. In analyses with UN and A models, it was recovered as paraphyletic, with Mylodontoidea closely related to Megatheriidae or Megatheriinae . When Megatherioidea was recovered as monophyletic, Pelecyodon and Schismotherium emerged as successive sister taxa of a clade containing megalonychids and megatheriids (H models, par_EW and par_IW100), or, together with Hapalops , composing a clade that is more closely related to megatheriids than to megalonychids (par_IW10 and par_IW5). When Megatherioidea was paraphyletic (A models), Pelecyodon and Schismotherium compose a sister clade to all other eufolivorans.

Megatherioidea was supported by 43 synapomorphies (18 for both methods and 25 exclusively for BI): left and right molariform toothrows parallel in occlusal view (BI); cementum slightly thicker than the orthodentine; occlusal surface of molariforms with strong transverse crests (BI); Mf4 curved anteriorly in lateral view; circular Mf1 crosssection (BI); mediolaterally ovate to rectangular mf1 cross-section (BI); mediolaterally ovate to rectangular Mf2 and Mf3 cross-section (BI); mediolaterally ovate to rectangular mf2 cross-section (BI); circular mf3 cross-section; inferior edge of mandible with strongly convex ventral bulge (BI); presence of a constriction at the junction of horizontal and ascending rami of mandible (BI); elongate and narrow angular process (BI); symphysis ending well anterior to the level of mf1; presence of symphysial keel (BI); symphysial spout equal to, or slightly shorter than the length of molariform toothrow (BI); eversion of lateral edge of symphyseal spout (BI); lateral edges of the spout converging anteriorly (BI); presence of a mandibular fossa posterior to cf1; roughly horizontal dorsal surface of the skull; temporal lines meet in the dorsal midline to form a sagittal crest; presence of fossa at the root of zygoma, anterodorsal to paroccipital process; presence of buccinator fossa of maxilla; presence of maxillary fossa behind last upper tooth; palate concave anteriorly, and convex posteriorly to dentition (BI); interpterygoid region broader than interpalatine region (BI); absence of pterygoid inflation (BI); presence of lacrimal eminence; anterior overlap of jugal and lacrimal over facial portion of maxilla; short and deep middle process of jugal (BI); tip of zygomatic process of squamosal at or posterior to frontoparietal suture (BI); presence of a marked postorbital constriction (BI); occipital condyle elongated anteroposteriorly, in ventral view; absence of a median ridge of basisphenoid (BI); ventral edge of entotympanic extended into anteroventral process; posteroventral stylomastoid canal (BI); rugose posterior surface of glenoid; well-developed entoglenoid process; convex posterior margin of ulnar diaphysis, in lateral view (BI); presence of deep notch for medial cruciate (posterior) ligament in femur (BI); equivalent transverse diameters of discoid and odontoid facets of astragalus, in dorsal view (BI); posterior surface of fibular facet of astragalus greatly reduced dorsoventrally (BI); roughly right-angled facets for cuboid and metatarsal IV, in metatarsal V; and laterally oriented expansion of metatarsal V.