Noise Annoys Not Mouriamorphs Filled a Niche THESE Days, Our Ears Are Too Sensitive for That Made Their Preserva Their Own Good
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NEWS AND VIEWS DAEDALUS--------~ An orthodox interpret ation might be that sey Noise annoys not mouriamorphs filled a niche THESE days, our ears are too sensitive for that made their preserva their own good. Primitive tribes, with only tion unlikely until the begin natural sounds to listen to, retain their ning of the acute hearing into late age. Modern Permian, at which point civilization, however, batters our ears into taphonomic circumstances early deafness. They have a natural changed and they were protection mechanism, but it badly needs suddenly abundantly pre upgrading. served, both in Euramerica It uses two tiny muscles, the tensor and in those plates newly tympani and the stapedius, which reduce accreting to Euramerica in the ear's sensitivity by stiffening the the Lower Permian. How joints of its transmission bones. They are ever, with tetrapods also tensed automatically by loud noise. They FIG. 2 Discosauriscus, a small, probably larval seymouri diversifying in East Gond worked well in prehistoric times, when amorph from the Lower Permian of the Czech Republic. Cal wana in the Early Carbonif most noises built up slowly. But they ibrated scale bar, 5 cm. (Science Museum of Minnesota; erous, it is equally possible photograph by A. M.) cannot react fast enough to modern that seymouriamorphs first bangs and crashes, and sustained uproar apparently centred on equatorial appeared there and, instead of spreading fatigues them. Daedalus wants to warn Euramerica, was largely a process of westwards, spread or hopped north across them of noise in advance. ecological niche-hopping within a s ingle the chain of North China, Tarim and A sound wave launched upwards into continent. The new material raises the Kazakhstan plates during the Upper the atmosphere, he notes, can be tracked possibility that different tetrapod groups Carboniferous (Fig. la), bursting onto the by radar. The density gradient of the diversified in parallel in different regions Euramerican scene in the Early Permian wave reflects the radar beam. So he is of the equatorial belt and subsequently when the Kazakhstan plate finally sutured scaling the idea down. He is devising a extended their geographical ranges, inter with Euramerica8 (Fig. lb). These alter little diode-radar placed next to the ear, acting with each other as they did so. natives are potentially testable, depending which scans the nearby air for the Given that we have a reasonably coherent on where well-dated Carboniferous sey density signature of an approaching Carboniferous-to-Lower Permian record mouriamorphs are ultimately demon noise. A mere metre of range would give only in Euramerica, we might look to it to strated to have occurred. D 3 milliseconds of advance warning, provide circumstantial evidence of immi ample time to tighten the defending gration of groups from elsewhere. This Andrew Milner is in the Department of Biol muscles against the coming crash. would manifest itself as the sudden ogy, Birkbeck College, Malet Street, London At first Daedalus intended to tense the appearance in the fossil record of abun WC1E 7HX, UK. muscles with a small electric shock, but dant or diverse distinctive groups with no soon realized that this would be more apparent antecedents or close relatives 1. Panchen, A. L. in Atlas o f Palaeobiogeography (ed. distressing than the noise itself. He then within Euramerica. The tetrapod group Hallam, A.) 117- 125 (Elsevier, Amsterdam, 1973). 2. Thulborn, A., Warren, A., Turne r, S. & Hanley, T. Nature recalled the odd fact that many people that most plausibly fulfils this criterion is 381, 777- 780 (1996). can hear audio-modulated microwaves. the Seymouriamorpha. 3. Warren, J. W. & Wakefield, N. A. Nature 238, 469-470 ear must be electronic (1972). The tissues of the The seymouriamorphs are agreed to be 4. Campbell, K. W. S. & Bell, M. W. Alcheringa 1 , 369- 381 rectifiers, able to demodulate a high close relatives of the true amniotes, al (1977). frequency carrier. Now high-frequency 5. Warren, A. A., Jupp, R. & Bolton, B. Alcheringa 10, though they retain gill-bearing larvae and 183- 186 (1986). currents are not painful. So Daedalus's lateral-line canals. The best-known genus, 6. Panchen, A. L. ln Major Patterns in Vertebrate Evolution 'Radar Earplugs' will react to loud sound Seymouria, was for many years considered (eds Hecht, M. K. , Goody, P. C. & Hecht, B. M.) 723-738 (Plenum , New York, 1977). by injecting a painless high-frequency to be the earliest reptile. Well-dated sey 7. Long, J. A. Lethaia 23. 157- 166 (1990). current into each ear, via electrode pads mouriamorphs first appear suddenly and 8. Milner, A. R. in Palaeozoic Vertebrate Biostratigraphy and strategically placed around the ear. The Biogeography (ed. Long, J. A.) 324- 353 (Belhaven, simultaneously in the earliest Permian of London, 1993). ear's gain-control muscles nestle in Euramerica (New Mexico, Utah, Texas, 9. Vorobyeva, E. I. & Schultze. H.-P. in Origins of the Higher insulating corridors of bone. Proper siting Groups of Tetrapods: Controversy and Consensus (eds France, Germany and the Czech Repub Schultze, H.-P. & Trueb, L.) 68- 109 (Comst ock. Ithaca, of the pads could funnel their current lic), with no Late Carboniferous relatives NY, 1991). largely through those muscles. They will whatsoever. Their consistent position on 10. Ahlberg, P. E. Nature 373, 420-425 (1995). 11. Carroll, R. L. Bull. Mus. natl Hist. nat., Paris 17, rectify the current and tighten in the recent cladograms (see ref. 11, for exam 389-445 (1995). resulting d.c., thus turning down the gain ple) implies that they were already been 12. lvakhnenko, M. F. Paleont. J. 1981(1), 90-102 (1981). before the racket arrives. They will keep it 13. Zhang, F., Li, Y. & Wang, X. Vertebr. palasiat. 22, present in the Early Carboniferous, and yet 294- 304 (1984). down as long as necessary - long after several rich Late Carboniferous vertebrate 14. Kuznetsov, V. V. & lvakhnenko, M. F. Paleont. J. the nerve serving them would have rel 1981(3), 101-108 (1981). assemblages in Euramerica include 15. Laurin, M. PaleoBios 16(4), 1-8 (1995). succumbed to fatigue. atives of almost every other Early Permian 16. Scot ese, C. R. & McKerrow, W. S. in Palaeozoic Radar Earplugs will be small and neat group, but no seymouriamorphs. Not only Palaeogeography and Biogeography (eds Mc Kerrow, W. S. & Scotese, C.R.) 1- 21 (Geol. Soc. Lond., 1990). enough to masquerade as earrings, or fit this, but populations of seymouriamorph on spectacle frames. You will hardly larvae ('discosauriscids'; see Fig. 2) are Erratum notice their action; your hearing will seem found in Permo-Carboniferous beds of im IN Laurence Hurst and Gi lean McVean's News just as acute. Yet sudden loud sounds will precise age on the Kazakhstan and Tarim and Views a rticle published last w eek (Nature cease to startle you, and sustained continental plates, in strata where no other 381, 650- 651; 1996), dealing with asexuality cacophony will seem far less fatiguing. the dia tetrapods have been found. Several of in endosymbiotic bacteria, the bars in Wear them regularly, and you will retain these central Asian 'discosauriscid' genera gram were incorrectly described in the caption. Blue shows the ratio of mean non-synonymous pin-sharp hearing well into senility - 12, 1 Utegenia 14) (A riekanerpeton Urumqia 3, to mean synonymous substitutions per nucleo unless you foolishly bypass your own have been named, and one of them, tide s ite in the endosymbiont Buchnera; red defences with a personal stereo. Utegenia, appears to be one of the most the ratio in the free-living enterics Escherichia David Jones primitive seymouriamorphs15• coli and Salmonella typhimurium. 742 NATU RE · VOL 381 · 27 JUNE 1996 .