Presentation on theme: "Order Carnivora ≥11 families, >287 species Naturally distributed on all continents (except possibly Australia) Morphologically & behaviorally diverse Economically."— Presentation transcript:
Order Carnivora ≥11 families, >287 species Naturally distributed on all continents (except possibly Australia) Morphologically & behaviorally diverse Economically important in most countries Ecologically important
Order Carnivora Recognition characters (most/all related to carnivory): Dental features (present in MOST species): Carnassial shear: P4/M1 (secondarily lost in some taxa) Canines large, conical Most have primitive # incisors (3/3) Cranial features: Transverse glenoid fossa Sagittal crest often prominent, well developed Large brains, well developed zygomatic arch Other features: Most are medium-sized Acute senses (hearing, sight, especially smell) Most are adept cursors---sprinting Simple stomach (cecum reduced or absent in most sp.)
Glenoid/ mandibular fossa C-shaped: strong hinge, minimizes lateral movement and facilitates up & down movement (e.g., mustelids) Omnivores (e.g., bears, procyonids) have more “open” glenoid fossa, permitting lateral movement
Postcranial modifications: loss or reduction of clavicles (increases stride length) fusion of carpal bones (may add support for cursorial locomotion)
Fusion of centrale, scaphoid, & lunar bones of wrist Carnivora Most non-carnivorans
Creodonts---Fossil carnivorans, late Cretaceous-Miocene Outcompeted by more “modern” carnivorans?
18 genera, 40 sp. All continents ‘cept Austr., Antarctica
Felids: “The ultimate killing machines” Most specialized hunters of the carnivorans, relying almost exclusively on prey that they have killed themselves. short rostrum=increased bite force at canines
Smilodon Thylacosmilus (extinct S. American hypercarnivorous marsupial) Hypercarnivory has evolved several times (and in several orders) Usually correlated with LARGE BODY SIZE...
Cope’s Rule:Evolutionary trend towards larger body size. Common among mammals. Advantages:-Avoid predators -Enhance reproductive success -Improve thermal effiency -Interspecific competition for food -Capture larger prey (prey size often increases over time)
Tradeoff between foraging effort & food acquired imposes energetic constraint. Smaller carnivores can subist on small prey (e.g., insects, rodents). Larger carnivores (> ca. 21 g)--small prey not worth the energy expended. Larger body size leads to HYPERCARNIVORY and overspecialization? Prey size (cont.)
Hypercarnivory in N. American canids Canidae---3 subfamilies Caninae Hesperocyoninae † (>28 sp.) Borophaginae † (>68 sp.) Diverse in Miocene; peak of 25 contemporaneous species. (compare with 7 extant canids in N.S. today) N. America endemics
1st appearance of hypercarnivorous hesperocyonines 1st appearance of hypercarnivorous borophagines Millions of years ago
“Constraint” Any factor that tends to slow the rate of adaptive evolution. Reversal to more generalized morphology rare in highly specialized taxa. Hypercarnivory may lead to “adaptive peak” that can’t be descended...