Echidna Development

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A personal message from Dr Mark Hill (May 2020)  
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I have decided to take early retirement in September 2020. During the many years online I have received wonderful feedback from many readers, researchers and students interested in human embryology. I especially thank my research collaborators and contributors to the site. The good news is Embryology will remain online and I will continue my association with UNSW Australia. I look forward to updating and including the many exciting new discoveries in Embryology!



The Echidna family consists of 2 major groups the short-beaked in Australia and long-beaked in New Guinea and Indonesia (Irian Jaya). Together with the platypus these are the only 3 surviving genera of the order Monotremata.

Echidna egg ultrasound[1]

The echidna is a unique egg-laying mammal, the embryo is referred too as a "puggle" (not to be confused with the dog breed, produced by mating a Pug with a Beagle) and is not a common animal model of mammalian embryonic development.

The New Guinea long-beaked echidna (Zaglossus bruijni bartoni) is currently on the endangered category (More? Zoo Threatened Species list)

Also see the Category:Echidna and these historic articles Historic - Monotremata and Marsupialia Embryology | Historic - 1915 The Monotreme Skull. The Hill Collection contains much histology of echidna embryonic development.

Australian Animal: echidna | kangaroo | koala | platypus | possum | Category:Echidna | Category:Kangaroo | Category:Koala | Category:Platypus | Category:Possum | Category:Marsupial | Category:Monotreme | Development Timetable | K12
Historic Australian Animal  
Historic Embryology: 1834 Early Kangaroo | 1880 Platypus Cochlea | 1887 Monotremata and Marsupialia | 1910 Eastern Quoll | 1915 The Monotreme Skull | 1939 Early Echidna

The Hill Collection contains much histology of echidna and platypus embryonic development.

Embryology History | Historic Disclaimer

Other Marsupials  
Monito del Monte Development | Opossum Development

Some Recent Findings

  • Frozen embryos? Torpor during pregnancy in the Tasmanian short-beaked echidna Tachyglossus aculeatus setosus[2] "We studied the interaction between torpor and reproduction in free-ranging female Tasmanian echidnas using a combination of techniques including urogenital smears, hormone analysis, ultrasonography, external temperature loggers and camera traps. Male echidnas initiated mating activity by locating hibernating females. All females that mated or were disturbed by males prior to July 27 re-entered hibernation, including many that were pregnant. Pregnant females only entered hibernation in early pregnancy when plasma progesterone concentrations were about twice basal and progesterone then remained constant during torpor. By re-entering hibernation pregnant females extended their gestation period and delayed egg-laying. Progesterone peaked 4-6days before egg-laying, then dropped rapidly."
  • Observations on fur development in echidna (Monotremata, Mammalia) indicate that spines precede hairs in ontogeny[3]"In the primitive mammal echidna, the initial 2-3 generations of skin appendages produced from birth forms spines and only later true hairs appear. Microscopy on preserved museum specimens reveals that the morphogenesis of spines and hairs is similar but that a larger dermal papilla is formed in spines. The growing shaft comprises a medulla surrounded by a cortex and by an external cuticle. A thick inner root sheath made of cornified cells surrounds the growing shaft inside the spine canal that eventually exits with a pointed tip. Hairs develop later with the same modality of spines but have a smaller papilla and give rise to a fur coat among spines. Therefore the integument of developing echidnas initially produces spines from large dermal papillae but the reduction in size of the papillae later determines the formation of hairs. Although the morphogenesis of spines and hairs can represent a case of specialization in this species, the primitive mammalian characteristics of echidnas has also inspired new speculations on the evolution of the mammalian hair from mammalian-like reptiles with a spiny coat. The resemblance in the morphogenesis between spines and hairs has suggested some hypothesis on hair evolution, in particular that hairs might be derived from the reduction of protective large spines present in ancient mammalian-like reptiles possibly derived from the reduction of pre-existing pointed scales. The hypothesis suggests that spines became reduced and internalized in the skin forming hairs."
  • Development of the hypothalamus‎ and pituitary in platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus)[4] "The Hill and Hubrecht embryological collections have been used to follow the structural development of the monotreme hypothalamus and its connections with the pituitary gland both in the period leading up to hatching and during the lactational phase of development, and to relate this structural maturation to behavioural development. In the incubation phase, development of the hypothalamus proceeds from closure of the anterior neuropore to formation of the lateral hypothalamic zone and putative medial forebrain bundle. In many respects, the structure of the hypothalamus and pituitary of the newly hatched monotreme is similar to that seen in newborn marsupials, suggesting that both groups rely solely on lateral hypothalamic zone nuclei for whatever homeostatic mechanisms they are capable of at birth/hatching."
  • Monotreme ossification sequences and the riddle of mammalian skeletal development[5] "Late femoral ossification with respect to tibia/fibula in monotremes and moles points toward developmental integration of the serially homologous fore- and hindlimb bones. Monotreme cervical ribs and coracoids ossify later than in most amniotes but are similarly timed as homologous ossifications in therians, where they are lost as independent bones. This loss may have been facilitated by a developmental delay of coracoids and cervical ribs at the base of mammals. The monotreme sequence, although highly derived, resembles placentals more than marsupials. Thus, marsupial postcranial development, and potentially related diversity constraints, may not represent the ancestral mammalian condition."
More recent papers  
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This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.

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More? References | Discussion Page | Journal Searches | 2019 References | 2020 References

Search term: Echidna Embryology

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Hibernation and reproduction overlap in the echidna.[1] "During hibernation there is a slowing of all metabolic processes, and thus it is normally considered to be incompatible with reproduction. ... The mating of males with torpid females is the result of extreme competition between promiscuous males, while re-entry into hibernation by pregnant females could improve the possibility of mating with a better quality male."
  • Characterisation of monotreme caseins[6] "...Overall, the conservation of the genomic organisation of the caseins indicates the early, pre-monotreme development of the fundamental role of caseins during lactation. In contrast, the lineage-specific gene duplications that have occurred within the casein locus of monotremes and eutherians but not marsupials, which may have lost part of the ancestral casein locus, emphasises the independent selection on milk provision strategies to the young, most likely linked to different developmental strategies. The monotremes therefore provide insight into the ancestral drivers for lactation and how these have adapted in different lineages."
  • Monotreme olfactory tubercle[7] "... The small olfactory tubercle region in the platypus is consistent with poor olfaction in that aquatic mammal, but the tubercle in the echidna is more like that of a microsmatic mammal than other placentals occupying a similar niche (e.g., insectivores)."
  • Sensory trigeminal nuclei of the echidna, platypus and rat.[8] "..... Our findings indicate that the trigeminal nuclei of the echidna do not appear to be highly specialized, but that the principal, oralis and interpolaris subnuclei of the platypus trigeminal complex are highly differentiated, presumably for processing of tactile and electrosensory information from the bill."


Short-beaked Echidna - Tachyglossus aculeatus

Long-beaked Echidna - Zaglossus bruijni

Tachyglossus aculeatus Lineage (full) cellular organisms; Eukaryota; Fungi/Metazoa group; Metazoa; Eumetazoa; Bilateria; Coelomata; Deuterostomia; Chordata; Craniata; Vertebrata; Gnathostomata; Teleostomi; Euteleostomi; Sarcopterygii; Tetrapoda; Amniota; Mammalia; Prototheria; Monotremata; Tachyglossidae; Tachyglossus

Echidna Zaglossus bruijn Lineage (full) cellular organisms; Eukaryota; Fungi/Metazoa group; Metazoa; Eumetazoa; Bilateria; Coelomata; Deuterostomia; Chordata; Craniata; Vertebrata; Gnathostomata; Teleostomi; Euteleostomi; Sarcopterygii; Tetrapoda; Amniota; Mammalia; Prototheria; Monotremata; Tachyglossidae

Development Overview

Gestation is from 22 to 23 days. (based upon 20 observed matings and documenting 30 incidences of egg laying, Rismiller, 1999).

Egg only a single egg is generally laid.

Incubation lasts for approximately 10 days after laying, the hatched embryo (puggle) requires further development.

Embryo after hatching hangs from hairs and succles from a "mammary gland" (mammary hairs) in the pouch for approximately 50 days and continues to develop.

Echidna historic embryology 01.jpg Echidna historic embryology 02.jpg

Historic drawings of Echidna embryology (1894).[9]


The oldest platypus and its bearing on divergence timing of the platypus and echidna clades.[10]

"Monotremes have left a poor fossil record, and paleontology has been virtually mute during two decades of discussion about molecular clock estimates of the timing of divergence between the platypus and echidna clades. ...Strict molecular clock estimates of the divergence between platypus and echidnas range from 17 to 80 Ma, but Teinolophos (Early Cretaceous fossil) suggests that the two monotreme clades were already distinct in the Early Cretaceous, and that their divergence may predate even the oldest strict molecular estimates by at least 50%."

Hill Embryological Collection

James Peter Hill (1873-1954) University of Edinburgh, Royal College of Science in London, 1892 demonstrator in Sydney, Australia. In 2004 this embryo collection was relocated to the Museum fur Naturkunde, Berlin.

Links: Hill Collection | Museum fur Naturkunde - Embryological Collection


  1. 1.0 1.1 Morrow G & Nicol SC. (2009). Cool sex? Hibernation and reproduction overlap in the echidna. PLoS ONE , 4, e6070. PMID: 19562080 DOI.
  2. Morrow GE, Jones SM & Nicol SC. (2017). Frozen embryos? Torpor during pregnancy in the Tasmanian short-beaked echidna Tachyglossus aculeatus setosus. Gen. Comp. Endocrinol. , 244, 139-145. PMID: 26562301 DOI.
  3. Alibardi L & Rogers G. (2015). Observations on fur development in echidna (Monotremata, Mammalia) indicate that spines precede hairs in ontogeny. Anat Rec (Hoboken) , 298, 761-70. PMID: 25367156 DOI.
  4. Ashwell KW. (2012). Development of the hypothalamus and pituitary in platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus). J. Anat. , 221, 9-20. PMID: 22512474 DOI.
  5. Weisbecker V. (2011). Monotreme ossification sequences and the riddle of mammalian skeletal development. Evolution , 65, 1323-35. PMID: 21521190 DOI.
  6. Lefèvre CM, Sharp JA & Nicholas KR. (2009). Characterisation of monotreme caseins reveals lineage-specific expansion of an ancestral casein locus in mammals. Reprod. Fertil. Dev. , 21, 1015-27. PMID: 19874726 DOI.
  7. Ashwell KW. (2006). Cyto- and chemoarchitecture of the monotreme olfactory tubercle. Brain Behav. Evol. , 67, 85-102. PMID: 16244467 DOI.
  8. Ashwell KW, Hardman CD & Paxinos G. (2006). Cyto- and chemoarchitecture of the sensory trigeminal nuclei of the echidna, platypus and rat. J. Chem. Neuroanat. , 31, 81-107. PMID: 16198535 DOI.
  9. Semon R. Zur Entwickelungsgeschichte der Monotremen. Denkschriften der Medizinisch-Naturwissenschaftlichen Gesellschaft zu Jena (Embryology of the monotremes. Proceedings of the Medical and Natural Sciences Society in Jena). (1894) 5: 61–74.
  10. Rowe T, Rich TH, Vickers-Rich P, Springer M & Woodburne MO. (2008). The oldest platypus and its bearing on divergence timing of the platypus and echidna clades. Proc. Natl. Acad. Sci. U.S.A. , 105, 1238-42. PMID: 18216270 DOI.


Rowe MJ, Mahns DA, Bohringer RC, Ashwell KW & Sahai V. (2003). Tactile neural mechanisms in monotremes. Comp. Biochem. Physiol., Part A Mol. Integr. Physiol. , 136, 883-93. PMID: 14667851

Musser AM. (2003). Review of the monotreme fossil record and comparison of palaeontological and molecular data. Comp. Biochem. Physiol., Part A Mol. Integr. Physiol. , 136, 927-42. PMID: 14667856

Belov K & Hellman L. (2003). Immunoglobulin genetics of Ornithorhynchus anatinus (platypus) and Tachyglossus aculeatus (short-beaked echidna). Comp. Biochem. Physiol., Part A Mol. Integr. Physiol. , 136, 811-9. PMID: 14667846

Temple-Smith P & Grant T. (2001). Uncertain breeding: a short history of reproduction in monotremes. Reprod. Fertil. Dev. , 13, 487-97. PMID: 11999298


Ashwell KW & Shulruf B. (2014). Vestibular development in marsupials and monotremes. J. Anat. , 224, 447-58. PMID: 24298911 DOI.

Selwood L & Johnson MH. (2006). Trophoblast and hypoblast in the monotreme, marsupial and eutherian mammal: evolution and origins. Bioessays , 28, 128-45. PMID: 16435291 DOI.

Ashwell KW. (2006). Cyto- and chemoarchitecture of the monotreme olfactory tubercle. Brain Behav. Evol. , 67, 85-102. PMID: 16244467 DOI.

Thorp BH & Dixon JM. (1991). Cartilaginous bone extremities of growing monotremes appear unique. Anat. Rec. , 229, 447-52. PMID: 2048749 DOI.

Keast JR. (1993). Innervation of the monotreme gastrointestinal tract: a study of peptide and catecholamine distribution. J. Comp. Neurol. , 334, 228-40. PMID: 8103529 DOI.

Manger PR, Fahringer HM, Pettigrew JD & Siegel JM. (2002). The distribution and morphological characteristics of cholinergic cells in the brain of monotremes as revealed by ChAT immunohistochemistry. Brain Behav. Evol. , 60, 275-97. PMID: 12476054 DOI.

Djakiew D & Jones RC. (1983). Sperm maturation, fluid transport, and secretion and absorption of protein in the epididymis of the echidna, Tachyglossus aculeatus. J. Reprod. Fertil. , 68, 445-56. PMID: 6864661


The Echidna: Australia's Enigma (Hardcover, 1999), by Peggy Rismiller (Amazon Link) "The oldest surviving mammal on the planet is also one of the most intriguing. Peggy Rismiller, the world's foremost echidna expert, traces the history of this fascinating animal that is native to Australia and New Guinea. A combination of mammal, reptile, and marsupial, echidnas produce milk, but unlike mammals, they are egg-laying creatures and, like marsupials, they have a modified pouch for nurturing their young. This odd animal has two backward-facing appendages and two forward-facing ones. These and other bizarre biological traits are discussed in detail in this thorough guide. Amazing photographs of echidnas enliven Rismiller's text, which includes Aboriginal tribal legends about the animal as well as the latest information on biological research being conducted today. With fossils dating back 120 million years, the echidna lived alongside dinosaurs, but unlike the giant reptiles, it survived. Its story and biology teach a fascinating lesson about endurance, survival, and sustainability."

American Museum Novitates (American Museum of Natural History) Van Deusen, H. M., and G. G. George. Results of the Archbold Expeditions. No. 90. Notes on the echidnas (Mammalia: Tachyglossidae) of New Guinea. American Museum Novitates, 2383:1-23 (1969)

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Search Jan2006 "Echidna development" 303 reference articles of which 20 were reviews.

Search PubMed: Echidna development | monotreme development

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Cite this page: Hill, M.A. (2020, August 11) Embryology Echidna Development. Retrieved from

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