It might be an obvious one for day "L" of but I Love the Legendary Loveable Latimeria chalumnae! This Coelacanth is:
• Critically per
Appendix I (Int'l is generally prohibited)
ESA Threatened (Tanzanian DPS)

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I think we're up to "I" in so it's time for Icarealcyon, a Triassic holostean (gar + bowfin relative) once thought to be able to glide with its broad pectoral fins.

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Another old drawing for the Devonian lungfish Griphognathus

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