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Ordinary baryons are bound states of 3 quarks. Exotic baryons are bound states of 3 quarks and additional particles. These additional particles can be quarks. The pentaquark, which consists of four quarks and an anti-quark, is the only exotic baryon that has claimed to have been detected. Another exotic baryon which consists only of quarks is the H di-baryon^{[1] [2]}. The H di-baryon consists of two up quarks, two down quarks and two strange quarks. Unlike the pentaquark, this particle can be long lived or even stable.

Several types of exotic baryons which require physics beyond the standard model have been conjectured in order to explain specific experimental anomalies. There is no independent experimental evidence for any of these particles. One example is supersymmetric R-baryons^[3], which are bound states of 3 quarks and a gluino. The lightest R-baryon is denoted as S⁰ and consists of an up quark, a down quark, a strange quark and a gluino. This particle is expected to be long lived or stable and has been invoked to explain ultrahigh energy cosmic rays^{[4] [5]}. Stable exotic baryons are also candidates for strongly interacting dark matter.

1. ↑  R. Jaffe, Perhaps a stable dihyperon..., Phys. Rev. Lett. 38, 195 (1977).
2. ↑  G. R. Farrar and G. Zaharijas, Nuclear and nucleon transitions of the H di-baryon, Phys. Rev. D 70, 014008 (2004) preprint.
3. ↑  G. R. Farrar, Detecting Gluino-Containing Hadrons, Phys. Rev. Lett. 76, 4111 (1996) preprint.
4. ↑  D. Chung, G. R. Farrar and E. W. Kolb, Are ultrahigh energy cosmic rays signals of supersymmetry?, Phys. Rev. D 57, 4606 (1998) preprint.
5. ↑ I. F. M. Albuquerque, G. Farrar and E. W. Kolb, Exotic massive hadrons and ultra-high energy cosmic rays, Phys. Rev. D 59, 015021 (1999) preprint.