Traditional view: Insectivorans represent primitive eutherian stock.
Original classification of Insectivora (mid-1800s): Elephant shrews Treeshrews Flying lemurs Erinaceidae Solenodontidae Soricidae Talpidae Chrysochloridae Tenrecidae Insectivora
Original classification of Insectivora (1866): Elephant shrews Treeshrews Flying lemurs Erinaceidae Solenodontidae Soricidae Talpidae Chrysochloridae Tenrecidae Cecum present: Order Menotyphla Cecum absent: Order Lipotyphla
Original classification of Insectivora (1900s): Elephant shrews: Order Macroscelidea Treeshrews: Order Scandentia Flying lemurs: Order Dermoptera Erinaceidae Solenodontidae Soricidae Talpidae Chrysochloridae Tenrecidae Cecum absent: Order Lipotyphla (but use of “Insectivora” continued)
Proposed synapomorphies (Butler 1988): 1.Maxillary expansion in orbit 2.Mobile proboscis 3.Reduced jugal 4.Hemochorial placenta 5.Reduced pubic symphysis 6.Cecum absent Lipotyphla Late 1900s: Is Lipotyphla a natural group?
1.Maxillary expansion in orbit (preventing contact of palatine & frontal) maxilla palatine frontal Hedgehog Opossum BUT, golden moles, some tenrecs don't have expanded maxilla.
2.Mobile proboscis present in some... absent in others... and PRESENT in many non-lipotyphlans
3.Reduced jugal BUT, small jugals in hedgehogs may represent ancestral condition in eutherians. Jugal reduction in other lipotyphlans not well understood.
Tenrecs, golden moles, hedgehogs, solenodons (& some primates, bats, rodents...) shrews, some moles
5.Reduced pubic symphysis connected with cartilage only; no bony fusion ilium pubis BUT, reduced symphysis found in most fossorial mammals. "Reduced" difficult to categorize.
small intestine large intestine Cecum: 1st part of large intestine 2 primary functions: 1)Microbial breakdown of partially digested food 2)Recover moisture from digesting food In general, faunivores have simple gut tubes (animal prey easier to digest). Ancestral eutherian condition uncertain.