Mongolepidida

{{Short description|Extinct order of sharks}}

{{Use dmy dates|date=August 2024}}

{{Automatic taxobox

| image =

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| fossil_range = {{Fossil range|427.4|416|earliest=Katian|Late Silurian-Early Devonian}}

| taxon = Mongolepidida

| authority = Karatajūtė-Talimaa, Novitskaya, Rozman & Sodov, 1990

| type_species =

| type_species_authority =

| subdivision_ranks = Families

| subdivision_ref =IRMNG (2023). Mongolepidida †. Accessed at: https://www.irmng.org/aphia.php?p=taxdetails&id=10434 on 5 August 2024

| subdivision =

• {{extinct}}Mongolepididae Karatajūtė-Talimaa, Novitskaya, Rozman & Sodov, 1990
• {{extinct}}Shiqianolepidae Sansom, Aldridge & Smith, 2000
• incertae sedis
• {{extinct}}Solinalepis Andreev, Coates, Karatajūtė-Talimaa, Shelton, Cooper, Wang & Sansom, 2016

| synonyms =

| synonyms_ref = {{citation needed|date=}}

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The Mongolepidida is an order of primitive elasmobranchs that lived during the Late Silurian and Early Devonian periods of Russia and Mongolia, with possible fragmentary remains dating back to the Katian epoch of the Late Ordovician (c.450 Ma). The three known genera are: Elegestolepis,{{Cite web|url=https://planetsharkdivers.com/elegestolepis/|title=Elestegolepis|website=www.planetsharkdivers.com|access-date=12 August 2020|archive-date=24 October 2020|archive-url=https://web.archive.org/web/20201024153546/https://planetsharkdivers.com/elegestolepis/|url-status=dead}} Mongolepis{{Cite web|url=https://planetsharkdivers.com/mongolepis/|title=Mongolepis|website=www.planetsharkdivers.com}} and Polymerolepis.{{Cite web|url=https://planetsharkdivers.com/polymerolepis/|title=Polymerolepis|website=www.planetsharkdivers.com}}{{Cite journal |last1=Andreev |first1=Plamen |last2=Coates |first2=Michael I. |last3=Karatajūtė-Talimaa |first3=Valentina |last4=Shelton |first4=Richard M. |last5=Cooper |first5=Paul R. |last6=Wang |first6=Nian-Zhong |last7=Sansom |first7=Ivan J. |date=2016 |title=The systematics of the Mongolepidida (Chondrichthyes) and the Ordovician origins of the clade |journal=PeerJ |volume=4 |pages=e1850 |doi=10.7717/peerj.1850 |pmc=4918221 |pmid=27350896 |doi-access=free }}{{Cite journal |last=Karatajùtè-Talimaa |first=Valentina |date=1 January 1995 |title=The Mongolepidida: Scale structure and systematic position |url=http://www.sciencedirect.com/science/article/pii/S0016699595800832 |access-date=14 August 2020 |journal=Geobios |series=Premiers Vertandébrandés et Vertandébrandés Infandérieurs |volume=28 |pages=35–37 |language=en |doi=10.1016/S0016-6995(95)80083-2|bibcode=1995Geobi..28...35K |url-access=subscription }}{{Cite journal |last1=Andreev |first1=Plamen |last2=Zhao |first2=Wenjin |last3=Wang |first3=Nian-Zhong |last4=Meredith Smith |first4=Moya |last5=Li |first5=Qiang |last6=Cui |first6=Xindong |last7=Zhu |first7=Min |last8=Sansom |first8=Ivan |date=13 February 2020 |title=Early Silurian chondrichthyans from the Tarim Basin (Xinjiang, China) |url=|journal=PLOS ONE |volume=15 |issue=2 |pages=e0228589 |doi=10.1371/journal.pone.0228589|pmid=32053606 |pmc=7018067 |bibcode=2020PLoSO..1528589A |doi-access=free }} They are only known from fragmentary placoid scales, so their appearance is unknown. The oldest of these scales have been dated back to the Ludlow epoch (427.4 Ma to 423 Ma), making the members of the Mongolepidida possibly the oldest sharks known to date.{{Cite web|url=https://paleobiodb.org/cgi-bin/bridge.pl?a=checkTaxonInfo&taxon_no=34423&is_real_user=0|title=The Paleobiology Database|website=paleobiodb.org|access-date=5 May 2016}}

Although the placoid scales of the Mongolepidida are accepted to be those of sharks, subtle differences in the scales suggest that they may have been quite different in appearance to modern sharks. It is not known what they looked like due to the fragmentary nature of the known remains.{{Cite web |url=https://sharkopedia.discovery.com/shark-topics/prehistoric-sharks/#interactive-timeline-of-shark-evolution |title=Prehistoric Sharks | Sharkopedia |access-date=12 August 2020 |archive-date=12 July 2018 |archive-url=https://web.archive.org/web/20180712122249/https://sharkopedia.discovery.com/shark-topics/prehistoric-sharks/#interactive-timeline-of-shark-evolution |url-status=dead }}