Platypus thought to be older than echidnas (Augee et al.Venom in modern platypus thought to be used by adult males to gain mating access to females (not defense).Common ancestor of platypus and echidnas was also venomous, possibly for defense (Whittington and Belov 2014).Likely during or before early Cretaceous (Rowe et al.2009 Nicol 2015)-large gap in the fossil record (Augee et al. Divergence between echidnas and platypuses difficult to estimate (Phillips et al.Only the lineage containing the echidnas and platypuses survived the Australian ‘marsupial invasion’ of the Eocene to early Cretaceous (Phillips et al.Echidna-like monotreme, Kryoryctes cadburyi, from the Cretaceous (Pridmore et al.Earliest monotreme, Teinolophos trusleri, emerged 130 mya (Rowe et al.Further fossil evidence needed for corroboration (Rowe et al.Divergence of egg-laying mammals and live-bearing mammals.Falsely labeled ‘primitive’ by early scientists-monotremes are highly specialized and successful in their ecological, reproductive, and life history niches (see Augee et al.Today, only one platypus species and four echidna species remain.Monotremes (egg-laying mammals) were once a more diverse group (Augee et al.Mallangong (Grant 2007 Bridges, undated)įossil history and evolutionary relationships.Platypus, duck-billed platypus (English) (Moyal 2001 Jackson and Groves 2015 Woinarski and Burbidge 2016 ITIS 2018).Variations and misspellings of Ornithorhynchus.Genus Ornithorhynchus (Jackson and Groves 2015).Ornithorhynchus paradoxus (Blumenbach, 1800) (Grant 2015 Jackson and Groves 2015).Platypus anatinus (Shaw, 1799) (Grant 2015).Historically, four subspecies proposed (Grant 2015).Genetic evidence may warrant division into subspecies (Grant 2015 Jackson and Groves 2015).Recognized as one species, Ornithorhynchus anatinus (as of July 2018) (Jackson and Groves 2015 ITIS 2018).The platypus caused much taxonomic debate in Europe in the late 1700s and early 1800s (Ritvo 1997 Hobbins 2015).Genus Platypus already assigned to a genus of beetles Ornithorhynchus accepted.Blumenbach (as Ornithorhynchus paradoxus, 1800) (Grant 2015) Independently described by George Shaw (as Platypus anatinus, 1799) and J.F.Venomous in platypus (adult males only).Spur on hind ankle is connected to a gland in the thigh.Milk expelled from milk glands, through pore openings.Extended period of early growth and physical development.Little development of outer ear (“pinna”).No teeth-have mouth pads made of keratin.Snout has mechanoreceptors and electroreceptors.Snout formed by elongated nasal bones and jaw bones.Body temperature lower (32 oC) than placental or marsupial mammals (37 oC).Generate body heat able to regulate body temperature.Similarities to other mammals (marsupials and placental mammals).Short-beaked echidna, Tachyglossus aculeatus.Only five living/extant species of egg-laying mammals (“monotremes”).
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