The rise of predation in Jurassic lampreys

Abstract

Lampreys, one of two living lineages of jawless vertebrates, are always intriguing for their feeding behavior via the toothed suctorial disc and life cycle comprising the ammocoete, metamorphic, and adult stages. However, they left a meager fossil record, and their evolutionary history remains elusive. Here we report two superbly preserved large lampreys from the Middle-Late Jurassic Yanliao Biota of North China and update the interpretations of the evolution of the feeding apparatus, the life cycle, and the historic biogeography of the group. These fossil lampreys’ extensively toothed feeding apparatus differs radically from that of their Paleozoic kin but surprisingly resembles the Southern Hemisphere pouched lamprey, which foreshadows an ancestral flesh-eating habit for modern lampreys. Based on the revised petromyzontiform timetree, we argued that modern lampreys’ three-staged life cycle might not be established until the Jurassic when they evolved enhanced feeding structures, increased body size and encountered more penetrable host groups. Our study also places modern lampreys’ origin in the Southern Hemisphere of the Late Cretaceous, followed by an early Cenozoic anti-tropical disjunction in distribution, hence challenging the conventional wisdom of their biogeographical pattern arising from a post-Cretaceous origin in the Northern Hemisphere or the Pangean fragmentation in the Early Mesozoic.

Colonization of the ocean floor by jawless vertebrates across three mass extinctions

“…The tempo of hagfish diversification contrasts with the pattern observed in lampreys, the only other living clade of jawless vertebrates [ 36 , 39 ], which include numerous regional radiations that have diversified over the past 100 million years [ 36 ]. In contrast, our time-calibrated phylogeny of hagfishes infers an average evolutionary interval of 31.6 million years of common ancestry for individual hagfish species, which is considerably higher than the corresponding values for cartilaginous and bony fishes [ 115 ] or the one-to-two-million-year divergences of most lamprey species pairs [ 36 ].…”

“…Presently, only two lineages of jawless vertebrates, lampreys and hagfishes, survive. The resolution of living jawless vertebrates relationships and divergence times is essential for understanding the evolutionary context of living vertebrate diversity [ 36 – 42 ], but these remain disputed [ 9 , 37 , 39 , 42 – 55 ]; only in the past few years have comparative genomic analyses provided strong support for a hagfish-lamprey sister relationship [ 45 , 48 ].…”

“…The hagfish body plan, which includes features like a poorly developed eye and skeleton, auxiliary hearts, and a single semicircular canal, departs so much from other vertebrates that this clade has often been placed as the sister to all other living vertebrate clades [ 35 , 42 , 49 , 53 , 64 ]. Most molecular, morphological, and combined evidence analyses posit that hagfishes are the sister clade of lampreys [ 9 , 37 – 39 , 44 – 48 , 51 , 52 , 65 – 68 ]. However, the interrelationships of hagfishes and the age of living hagfish diversity remain underexplored [ 37 , 38 , 40 , 43 , 69 ].…”

“…However, the interrelationships of hagfishes and the age of living hagfish diversity remain underexplored [ 37 , 38 , 40 , 43 , 69 ]. This problem is compounded by the poor fossil record of the two living jawless vertebrate clades [ 36 – 39 , 64 – 67 , 70 – 74 ]; only a handful of fossils with well-characterized anatomy are identifiable as early total clade lampreys and hagfishes, and many fossil taxa identified as putative stem-group hagfishes and lampreys [ 75 ] may not even be jawless vertebrates [ 76 – 78 ].…”

The Life and Death of Jamoytius Kerwoodi White; a Silurian Jawless Nektonic Herbivore?

“…The fossil evidence for early evolution of lampreys is scanty because only four undoubted Palaeozoic parasitic lamprey species have been recorded, the above Devonian Priscomyzon, and three from the Carboniferous (359-299 Ma). These lack, however, the specialised, heavily toothed discs with plate-like laminae present in modern lampreys, and it is possible that they were grazers, scraping algae off surfaces (Wu et al, 2023). Furthermore, their post-Paleozoic fossil record of lampreys is equally bad.…”